FBI Links Recent Scholar Bombings to Past Cases : Investigation: Forensics experts are ‘certain’ attacks are the work of a terrorist who has emerged from a six-year hiatus.

Federal law enforcement officials said Friday that they are “very, very certain” the two bombs that injured professors at UC San Francisco and Yale University this week are the work of a terrorist who has re-emerged from a six-year hiatus after 12 similar bombings from 1978 to 1987.

“The forensic experts believe . . . that the maker or makers of each of these 14 explosive devices is the same person or persons,” Milton Ahlerich, the FBI’s special agent in Connecticut, said at a New Haven news conference.

“It’s been a long time since we heard from him--or them,” Jim Cavanaugh, deputy chief of the explosives division of the U.S. Bureau of Alcohol, Tobacco and Firearms, added in Washington.

Officials said they also suspect that the bomber may have strong ties in California, particularly Sacramento, where the only fatality caused by the bombs occurred in 1985.

Both bombs this week were sent through the mail and bore Sacramento postmarks--as was a boastful letter sent to the New York Times that was apparently written by the perpetrator, officials said.

The latest victim, David Gelernter, 38, a Yale associate professor of computer science was injured Thursday when he opened a package in his office.

Two days earlier, UC San Francisco geneticist Charles Epstein, 59, lost several fingers and suffered burns, cuts and injuries to his chest, abdomen and face when he opened a parcel in the kitchen of his home in Tiburon, on the north side of San Francisco Bay.

Investigators have not talked at length to either victim because of their conditions. Epstein’s medical condition was upgraded to stable, but he remains hospitalized. Gelernter was still on a respirator Friday, recovering from surgery.

Law enforcement authorities said they are sure of the link between this week’s bombings and the earlier 12 because of the use of the initials “FC” in the June 21 letter to the New York Times. The same initials had been crudely scratched onto some of the earlier bombs, sources said.

“We don’t know what that means, but it’s the first time that it’s been put out there by someone claiming responsibility,” Cavanaugh said, referring to the letter, which identified its author or authors as “an anarchist group calling ourselves FC.”

Ahlerich urged professors and scientists across the country to be wary of suspicious parcels, saying that, on average, the explosives have come in packages that measure roughly 8 inches by 11 inches and are 2- to 3-inches-thick.

Some of the bombs were mailed, often with excess postage, but others were simply left at the scene, officials noted.

Forensic experts believe that the bombs are linked because they all had the same “unique” qualities, said Rick Smith, an FBI spokesman in San Francisco.

“The bombs really show an obsessive attention on the part of the maker to the way various components work,” added Christopher Ronay, chief of the FBI’s explosives unit in Washington, who has investigated the bombings since 1982.

At one point during the 1980s, some investigators referred to the perpetrator as the “Junkyard Bomber” because of a tendency to fashion components from makeshift materials and scrap, according to retired Sacramento Sheriff’s Lt. Ray Biondi, who investigated the Dec. 11, 1985, bombing death of Hugh Scrutton, 38.

Scrutton, the owner of a computer rental store near Sacramento State University, picked up a burlap bag in the alley behind the store, setting off an explosive device.

Tensions ran high Friday at UC San Francisco. Police Chief Ron Nelson canceled days off for all 25 of his patrol officers, and flyers advising caution were distributed to all university departments.

UC Berkeley--site of two earlier bombing incidents--was also on “heightened alert,” according to campus spokesman Bob Sanders.

UC Irvine likewise sent a memo to all faculty and staff members on campus and at the UCI Medical Center in Orange, warning them to give “extra scrutiny” to all their mail at home and in the office.

Lynn McLeod, special assistant to UCI’s vice chancellor of administration, said the safety alert was distributed Thursday afternoon. It describes envelopes and packages that should be considered suspicious, including mail of foreign origin or that is addressed with misspellings of common words or incorrect titles or that has excessive masking tape or other securing devices or that has protruding wires or foil.

The memo says that UCI employees troubled by mail that shows these characteristics should contact the sender to find out more information about the contents and, if the employees are still uneasy, they should contact the campus police department.

Investigators said the latest bombings caught them by surprise because they had presumed that after six years of silence, the bomber had died, gone to jail for other crimes or given up.

There had been gaps of up to three years between previous bombings, so the case had not been abandoned, officials said. A federal task force continued to meet about once a year, the most recent such session taking place in a San Francisco hotel last summer.

In all, 21 people were injured in the previous string of bombings, which included incidents on the campuses of the University of Illinois-Chicago in 1978, Northwestern University in 1979, Vanderbilt University in 1982, UC Berkeley in 1982 and 1985 and the University of Michigan in 1985. A similar explosive device was found, but safely defused, in a University of Utah classroom in 1981.

FBI officials in San Francisco said law enforcement officials refer to the incidents as UNABOMB, which stands for United Airlines Bomb--a reference to a June 10, 1980, mail bombing that injured United Airlines President Percy Wood at his Lake Forest, Ill., home.

Two other incidents also involved the airline industry. On Nov. 15, 1979, a parcel detonated in the cargo bay of an American Airlines flight from Chicago to Dulles International Airport outside Washington. About a dozen passengers were treated for smoke inhalation after the plane made an emergency landing.

Investigation of that incident caused officials to recognize the similarity of the airplane bomb and the first two bombs, at the University of Illinois and Northwestern, Ronay said.

A big potential break in the bombings came on Feb. 20, 1987, when a witness saw a man setting a burlap bag down near a parked car in a Salt Lake City parking lot. Before the witness could investigate, another passerby picked up the bag and a bomb went off.

Authorities developed a sketch of the suspect based on a description provided by the witness, but there were no more bombing incidents until this week. The suspect is described as a medium-build white man with reddish-blond hair and a thin mustache.

Officials said they do not have any strong possible motives for the bombings, or any credible theories to explain the hiatus.

“It’s anybody’s guess,” Ronay said. “But we believe that his selection of targets may depend on his state of mind.”

By Friday, several hundred federal agents, assisted by state and local law enforcement officials, joined the search, rejuvenating the UNABOMB task force.

Times staff writer Leslie Berkman contributed to this story.