NEW HAVEN, Conn. (AP) - Investigators searched a bomb-damaged classroom at Yale University's law school Thursday to determine exactly what caused the explosion and how explosives got into the unoccupied room.
No one was injured when the bomb went off Wednesday afternoon, but the blast knocked down a partition between the classroom and an alumni lounge and sent smoke through the law school.
"I saw a huge fireball come out to the middle of the hallway," said law student Bob Hoo, who was standing in a ground floor hallway when the bomb exploded about 4:40 p.m. "It was an instantaneous blast. It was there and then it was gone."
Authorities said they did not yet know what the bomb was made of, who set off the device or why it was put there.
Michael J. Wolf, special agent in charge of the FBI in Connecticut, said there were no threats made before the explosion and no claims of responsibility afterward. There was no indication that it was an act of international terrorism, two U.S. officials familiar with intelligence information told The Associated Press on condition of anonymity.
Acting Police Chief Francisco Ortiz said investigators would be looking for anything symbolic about the blast - whether the date, room or anything else about the law school could be meaningful to the bomber.
Most Yale undergraduates had already left for the summer break by Wednesday, but there were a number of people in the law school building, where some students took final exams.
The building also houses a day care center and some residences. It was not clear whether any children were in the center at the time; residents were not being permitted to return Wednesday evening.
Some students who were in the building at the time of the explosion said they were being questioned by the FBI. Explosive-sniffing dogs were also brought in to search the law school and other buildings.
"It's going to take us approximately two to three days to fully process that scene, to find out type of explosive device was used and things like that," said Col. Timothy Barry, commander of the state police.
The classroom partition that was knocked down by the blast was made of wood and wallboard, and some portraits hanging from it were still intact after the explosion, officials said.
An official at the Department of Homeland Security, speaking on the condition of anonymity, told The Associated Press late Wednesday that authorities believe a bomb detonation caused the damage.
"When we recover pieces of the device we will be better able to put a label on it," state police spokesman Sgt. J. Paul Vance said Thursday.
The law school will be closed Thursday and Friday. But commencement will take place as scheduled in the building on Monday, university spokesman Tom Conroy said.
Yale's undergraduate commencement exercises are also scheduled for Monday.
The incident came as the nation was on elevated alert for possible terrorist attacks and several hours after President Bush - a Yale alumnus - visited the state to speak at the U.S. Coast Guard Academy graduation ceremony in New London, about 50 miles to the east.
One of the president's daughters, Barbara, is an undergraduate at Yale. John Gill, a Secret Service spokesman, said Barbara Bush "was not in danger at any time and she was not in the vicinity" of the blast.
A Yale professor, David J. Gelernter, was seriously injured June 24, 1993, when a mail bomb exploded in his campus office. Unabomber Theodore Kaczynski was sentenced in 1998 for that and numerous other attacks that killed three people and injured 23 from 1978 to 1995.
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