A bomb exploded on the first floor of the Sterling Law Buildings Wednesday afternoon, injuring no one but causing significant structural damage to two law school rooms, University administrators said.

University Secretary Linda Lorimer said officials are considering adding extra security for this weekend’s Commencement activities.

Police officers evacuated faculty and students from the Law School to the Broadway area and diverted traffic away from the section of York Street between Grove and College streets. The entire block around the Law School was cordoned off.

Students housed in the building were given temporary housing in Ezra Stiles College, Lorimer wrote in an e-mail to Yale students, faculty and staff.

The explosion came at 4:40 p.m., less than 24 hours after officials at the Department of Homeland Security raised the nation’s terror alert status to orange, the second highest level. A spokeswoman for the FBI in New Haven said members of the agency’s Joint Terrorism Task Force had been dispatched to the scene.

New Haven Mayor John DeStefano Jr. said at a press conference Wednesday evening that there was no evidence that the explosion was an act of terrorism.

Though access to Law School classrooms is officially limited to those with University key cards, Lorimer said the building was open all day and anyone could have walked in. Police have not announced any suspects and are investigating the incident.

Gabriel Sanchez LAW ’05, said he was in the bottom floor of the library and saw the ceiling collapsing in the computer room.

“We just got out through the emergency exits,” Sanches said. “It actually felt like an earthquake.”

Timothy Schnabel LAW ’05, who was in the lounge on the first floor, said he heard a loud sound and saw flames and dust. He said he saw a wall fall down between Room 120 and the Alumni Reading Room. Portraits of presidents Gerald Ford LAW ’41 and Bill Clinton LAW ’73, and Guido Calabresi ’53 LAW ’58 hung on that wall, said Adam Haslett LAW ’03.

Robert Snodgrass LAW ’03 said he was walking in the hallway next to the alumni reading room on the first floor when he felt the blast.

“It was more force than any I’ve ever felt,” Snodgrass said. “Wood flew out of the reading room and other people saw orange flame.”

Even students on the top floors of the building said they were able to feel the effects of the explosion.

“The floor jumped,” said Ashley Walker LAW ’05, who was in a reading room on the third floor when the bomb went off. “Ten or 20 seconds later, the alarm went off.”

She said people immediately left the building, passing through smoke on their way out.

Lorimer said the Law School will be closed for the rest of the week. Law School exams, which began this Monday, will continue as scheduled, but will be moved to Sheffield-Sterling-Strathcona Hall.

Although most students have left for summer vacation, Yale College seniors and other students preparing for the May 26 University Commencement are still on campus.

— Staff reporters Steven Sun and Lindsey Mergener contributed to this story.

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