Unabomber Tips Pour In; Security at LAX Still Tight : Manhunt: High-tech firms listed in letters’ return addresses heighten focus on N. California. Scrap metal dealers scrutinized as possible sources of bomb materials.

In the search for the elusive terrorist known as the Unabomber, federal authorities are being deluged with calls from tipsters--as many as 500 leads a day--but there was no indication Friday that they were any closer to finding their quarry.

While more than 100 agents from the FBI, the U.S. Postal Service and other federal agencies hunkered down sorting through potential leads, airport security remained tight as thousands of passengers headed to Los Angeles International Airport for the long holiday weekend, despite initial threats by the Unabomber in a letter to a San Francisco newspaper to blow up an airplane by July 4.

“We think things are going well here, even with the heightened security,” Airport Executive Director Jack Driscoll said Friday afternoon. “There [have] been no delays, in terms of traffic.” He said about 130,000 people a day are expected at the airport over the long weekend, up from the usual 100,000 to 110,000.

The scare was dissipated somewhat by a letter to the New York Times in which the serial bomber announced that his LAX threat was just a prank to remind the nation of his presence and his message.

But because the letters were sent on the same day, law enforcement officials were struggling to deal with their contradictory messages and were not canceling their security measures yet.

“We know he lied in one of the letters,” said one law enforcement source. “The question is: which one?”

The bomber’s threat originally had specified a six-day period in which the attack might occur. And though officials were not clear when the six-day countdown began, the clock is clearly running out and plans are in place to begin curtailing some of the law enforcement presence at the airport over the next few days.

Authorities continue to focus their search in Northern California in a broad area that includes San Francisco, where the investigation is headquartered, and this Central Valley city, known as home to contentious politicians but not violent extremists.

The bomber’s last victim was a Sacramento timber industry executive, and several of the Unabomber’s recent flurry of letters used Northern California return addresses or carried San Francisco postmarks. Suspected of mailing 16 bombs that killed three people and injured 23 others, he was code-named the Unabomber by law enforcement officials after early attacks on universities and airlines.

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Even before the latest airplane bomb threat, FBI agents were questioning owners and managers of scrap yards, asking a wide range of questions about their customers, employees and sales of small amounts of scrap lead and other metals.

Several scrap dealers said that investigators were asking about employees who may have come from Chicago or Salt Lake City, sites of bombings that have taken place during the Unabomber’s 17-year reign of terror.

The agents carried the widely distributed composite picture of a suspect, which was based on an eyewitness report in the 1987 bombing of a Salt Lake City computer company.

One San Leandro scrap metal dealer said that FBI agents showed him a second picture as well. The grainy black-and-white picture, showing a somewhat heavier man in an Army-type jacket, might have been a blow-up of a surveillance camera photo or a computer-generated image, said Elton J. Kantor, owner of Alco Iron and Metals Co.

Kantor said that the FBI agents would not allow him to make a copy of the second photo. “They did not want it out,” he said.

One federal law enforcement source confirmed that in addition to the now-familiar composite picture, which is outdated, agents now have more detailed sketches as well.

The source, who asked not to be identified, would not say why the newer drawings have not been released or how they were made. In the past, agents have cautioned that the Unabomber probably looks older than the 1987 composite.

“This guy is about as professional as anybody I’ve ever seen in my career,” the law enforcement source said. “He covers his tracks. He knows how to do it. He’s not the run-of-the-mill bomber. He has Timothy McVeigh [a suspect in the Oklahoma City bombing] so far outclassed, it’s not funny.”

At a number of scrap yards, FBI agents were seeking information about purchases of even small amounts of lead, zinc and magnesium as well as lead-coated wires--all potential components in the handcrafted package bombs that are the signature work of the Unabomber.

“They were going to yards that handled large quantities of scrap. They asked us if we had any employees from the Chicago area and also from Salt Lake City,” said Niles Rawls, manager of A-1 Metals in the town of Rio Linda, near Sacramento. Like the other dealers interviewed, Rawls said he could not help the agents.

Mark Logan, special agent in charge of the San Francisco office of the Bureau of Alcohol, Tobacco and Firearms and part of the federal Unabomber task force, explained that agents have pounded the pavement trying to match components of past bombs with supply sources.

Although the Unabomber handcrafts his bombs, often making wood parts, the most likely match will come from unusual metals he has used in the devices. Logan did not specify what those unusual metals might be.

Several scrap dealers said that they were asked about purchasers of magnesium, a metal that can be burned and can add to the damage inflicted by a bomb. But Logan would not comment on the metal content of the Unabomber’s devices.

“We’re trying to match up metal, trying to match up wood, any type of materials that have been used,” Logan said. “The FBI, ATF and postal [inspectors] are going out in teams to try to match up materials that have been used.”

The Unabomber has used explosive materials that are generally available, such as those employed in demolition, or smokeless powder that could be obtained for reloading ammunition or taken from fireworks. Some of his devices also have contained the explosive aluminum nitrate.

“The materials used in various devices are out there for anyone to get,” Logan said.

Logan said the investigation is a “massive, massive” effort. “It’s a continuous thing. We’re following leads, trying to rule in and rule out possibilities.”

Two Northern California high-tech companies, Calgene in Davis and GSS Array Technology Co. Ltd. in San Jose, found themselves enmeshed in the Unabomber case when they were listed as return addresses on his letters to newspapers.

Both firms are cooperating with authorities and have no idea why the Unabomber singled them out in his correspondence.

The inclusion of the company names in the addresses has caused dismay in the state’s high-tech industry.

“We are incredibly aware of this guy, group, or whatever it is,” said one Silicon Valley insider. “We are trying to keep ourselves out of the media so we don’t set ourselves up as a target. I wouldn’t be surprised if there isn’t a company in the Valley that isn’t taking extra precautions these days.”

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At Calgene, a firm that produces genetically engineered plants, spokeswoman Carolyn Hayward said the company was informed Wednesday that the Unabomber used its address in his correspondence with the New York Times. “We told the FBI we will cooperate fully,” she said.

At the San Jose offices of GSS Array Technology, a Bangkok, Thailand-based printed circuit board manufacturer, the mood was tense. The name and a former home address of chief financial officer Boon Long Hoe were used as the return address on a package mailed to the Washington Post.

A woman answering the telephone for Hoe at GSS who would only give her name as Arlene said the executive was traveling on business. “He has not left because of this incident,” she said, declining to offer any further comment. Arlene said she had been directed by the company president to field all press calls.

Neither firm appeared to know why it had been singled out.

In packages sent to both the New York Times and the Washington Post this week, the Unabomber wrote that he would end the killing if a respectable publication would print a 35,000-word treatise espousing his views on the evils of the modern “industrial-technological system.”

In his letters, he said he would give the papers three months to commit to publishing the work as well as regular follow-up messages.

Executives from both papers have said that they are still weighing their decisions and would not comment beyond initial statements released earlier in the week.

However, a senior reporter at the Washington Post said: “Everyone wants to save lives, but if we publish, where does it stop? What’s to prevent a kidnaper next week from saying, ‘I’ll release the little girl if you publish my treatise’?”

The terrorist threat caused a disruption of mail throughout California during the week. By Friday, the post office had augmented its crews of postal inspectors monitoring outgoing mail at 23 distribution and processing centers across the state with volunteer clerks, mail handlers and other employees, who were being trained in what to look for. In the past, the Unabomber has been known to favor stamps with the image of Eugene O’Neill and to use the word wood in the return address. But postal officials declined to specify if those or other characteristics were considered suspect.

Generally, window clerks are trained to look for obvious signs that something is amiss--a package that is ticking, leaking oil or has much more postage than necessary.

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Parcels, and priority and express mail from known shippers, such as large companies, were continuing to be accepted, Los Angeles post office spokesman David Mazer said. But that mail was to be shipped on planes owned by or under contract to the postal service, not on commercial craft.

Postal officials also were urging individuals to monitor their own mail, and to be wary of letters or packages from unknown shippers or addresses.

Dan Mihalko, a spokesman for the postal inspector in Washington, D.C., said a million-dollar reward posted in 1993 has generated thousands of leads. And more are continuing to come in and are being investigated.

“It’s been pretty much a full-court press since 1993,” he said, “but we’re still looking for that lead that leads us to him.”

FBI officials in San Francisco, where the investigation is headquartered, were overwhelmed with the public response to their request for information.

“We’ve got to take it one day at a time,” said FBI spokesman George Grotz. “We’ll respond to the leads as they’re coming in. Since the first day, we’ve had between 300 and 500 [calls daily]. The majority of them are viable leads.”

Others pointed out that every member of the law enforcement team is anxious to contribute to the capture of the culprit.

“It’s everybody’s dream to be able to catch this guy,” said one federal law enforcement source. “This guy has been doing this for 17 years. He’s killed three people. . . . Everybody wants a piece of this guy.”

Also contributing to this story were Times staff writers Richard Lee Colvin, Eric Lichtblau, Josh Meyer and Adrian Maher in Los Angeles; Mark Gladstone and Jenifer Warren in Sacramento; Julie Pitta in San Francisco, and Ronald Ostrow, Robert Jackson and James Bornemeier in Washington.