TERROR IN OKLAHOMA CITY : Hoaxes Plague U.S. Amid Tighter Security : Bombing: 15 federal buildings, Boston subway system and Redondo Beach Pier are targets of false threats. Man is arrested in local incident.

With the devastating blast in Oklahoma City still fresh in their minds, law enforcement officials across the country continued to be plagued by bomb threats Thursday.

For the first time since the 1991 Persian Gulf War, roadblocks, extra security guards, metal detectors and bomb-sniffing dogs appeared at federal buildings, airports, border crossings and military bases nationwide.

In the Southland, police arrested a man who allegedly made a bomb threat that prompted the evacuation of the Redondo Beach Pier and its shops for nearly three hours.

A caller on the WeTip crime hot line told police that someone had built an explosive device and planned to plant it at the pier, said Redondo Beach Police Sgt. Avery Richey.

A short time later, a man called from the pier and said he had planted the bomb, prompting police to clear the pier and the commercial area around it about 11 a.m.

“We did a thorough search of all the shops and the pier, over and under,” Richey said. “We had divers looking in the water and everything. We didn’t turn up anything.” The pier was reopened shortly before 2 p.m., he said.

At least 15 federal buildings scattered across the country were briefly evacuated after receiving “copycat” bomb threats that turned out to be hoaxes, authorities said.

Hoax “bombs” were left outside federal office buildings in San Francisco and suburban Seattle, leading to evacuation of the Seattle facility, officials said. A federal building in Oakland was also evacuated because of a bomb scare.

Mary Filippini, a spokeswoman for the U.S. General Services Administration, which oversees security at federal government offices, said that “what looked to be a device” was found near the San Francisco federal building Thursday morning.

The bomb squad was called in to examine the object, but it “turned out to be a hoax,” Filippini said, adding that the device consisted of “two bottles filled with a liquid with a timing device across the top.”

A similar package consisting of a plastic water bottle with a threatening message stenciled onto it was found outside the General Services Administration’s regional headquarters in Auburn, Wash., south of Seattle, police said.

The message referred to the federal raid two years ago on the Branch Davidian compound in Waco, Tex.

The package was destroyed by a police bomb squad, and the building was reopened.

Someone called in a bomb threat to the Oakland federal building Thursday morning, but the building was checked and nothing was found, Filippini said.

Soon afterward, the same building was evacuated and the bomb squad was called in after a suspicious object was spotted in the basement, Filippini said.

*

Oakland Mayor Elihu Harris said the object turned out to be an ordinary suitcase. About 3,500 people work in the Oakland building.

In Boston, police closed the city’s subway system for more than an hour because of a bomb scare that turned out to be a hoax, police said.

A police spokeswoman said a man telephoned the police at 11:55 a.m. EDT and said a bomb was set to explode about 1 p.m. at the Downtown Crossing station underneath the Filene’s Basement department store.

Police found no trace of a bomb during a search of the station.

On Wednesday, at least 16 bomb scares prompted Boston authorities to evacuate at least nine buildings, including City Hall and the John F. Kennedy Federal Building. Police found no bombs.

In New York, more police than usual were guarding government buildings and landmarks after Mayor Rudolph W. Giuliani put the city on heightened security alert.

Police briefly evacuated the international arrivals terminal at John F. Kennedy International Airport to examine suspicious items of luggage, but nothing was found, officials said.

*

“There were two items of suspicious luggage, but the area has been secured,” said spokeswoman Carmen Curci of the Port Authority of New York and New Jersey, which manages the airport. “Police evacuated the west wing for about 40 minutes after the unattended luggage was found at 8.30 a.m.”

Police in Washington, D.C., reported a surge of bomb threats. The offices of one television network bureau were briefly evacuated while the police bomb squad searched its offices.

Traffic reporters in Washington, which has the heaviest concentration of federal workers, reported that the flow to work appeared to be normal Thursday morning, suggesting that few were scared off.

Parents continued to drop their children at day-care facilities in government buildings, despite the gruesome pictures of dead and injured children being taken from the Oklahoma City building, which had a day-care center.

Ona Whitfield, who runs a day-care facility at the Labor Department, said most of the children showed up. “I do have some parents who are concerned,” she said. “But I guess they have to work.”

Reporters entering federal buildings Thursday morning said all bags and briefcases were checked, even for those with building passes. Police were out patrolling the streets nearby with orders to be on the lookout for suspicious cars.

Couriers were banned from entering buildings and ordered to leave their packages at X-ray machines. Extra guards were called in on overtime at several facilities.