In the wake of the shooting deaths of 33 people at Virginia Tech on Monday, colleges and universities around the nation were reviewing their security procedures and trying to reassure their communities.

Officials at the University of Oklahoma announced that all dorm buildings would be locked 24 hours a day until the end of the semester. Previously, they had only been locked at night.

Tuesday, reports from the campus in Norman, Okla., said that residence halls and large academic buildings were locked down briefly, though restrictions were soon lifted.

In an e-mail to the campus, university President David Boren said the situation may have been caused by a mistaken report near the student fitness center. A later e-mail said that the person who was spotted carrying something contacted authorities. He had been carrying an umbrella, according to Boren.

"It is now believed that the person was possibly carrying a yoga mat which was mistaken for a weapon," he said.

At Temple University in Philadelphia, officials told television station WCAU the school does everything it can to make sure tragedies don't happen there. Carl Bittenbender, Temple's executive director of campus security, said he feels one of the campus's strengths is the sheer size of the campus police force.

The school has 125 officers, 450 security cameras and its campus safety is integrated with the Philadelphia Police Department's 911 system.

"So, in any kind of major incident, there's a joint response. There's a joint response between campus police and Philadelphia police," Bittenbender said.

Indiana University police Capt. Jerry Minger told Indianapolis television station WRTV that he thinks the department is as prepared as it can be for such a situation.

"We work and train to address those kinds of situations. So, if the situation arises, we will do what we've been trained to do," Minger said.

IU police have had recent training on how to handle someone with a gun, shooting at or threatening students.

Florida State Univessity police Chief David Perry said his agency tries to be proactive and take steps to head-off a tragedy like the one that occurred Monday.

But he and others at an Atlantic Coast Conference security conference admitted there is no way to make a campus totally safe.

Virginia Tech is a member of the ACC, but officials did not attend the conference.

In Boston, home to more than 30 colleges and universities, some students told that while they appreciate security, they wouldn't want to feel like their school was a prison, where surveillance cameras and metal detectors were everywhere.