COLLEGE STATION, Texas -- A 40-foot pyramid of logs being assembled for Texas A&M's annual bonfire collapsed early Thursday while dozens of students were climbing on it. At least five students were killed and 25 injured.

In the hours after the 2:30 a.m. collapse, rescuers pulled four students from the rubble alive, said Bart Humphreys, a fire department spokesman. One student wasn't pulled free until more than six hours later.Even after that, Cynthia Lawson, a spokeswoman for the university, said crews could hear "moaning and tapping sounds," leading them to believe one or more students was still trapped.

At midmorning, cranes were removing logs gingerly, one by one, in the search for more students.

"Every piece of wood in that pile is unstable and every piece of wood that moves affects other pieces of lumber," Humphreys said.

Students who had been looking forward to the huge bonfire, a tradition since 1909 to get fans ready for the football game against archrival University of Texas, were instead in mourning.

Some gathered near the scene, a field on the northeast corner of the campus, holding hands and praying while the rescue efforts continued.

"The scene right now is a scene of disbelief," said Sallie Turner, editor of the Battalion, the student newspaper. "A lot of the students just feel it's surreal."

Twenty-five students were taken to hospitals, university President Ray Bowen said. He said there were four dead, and a law enforcement source said at least one other person was dead inside the wreckage.

Officials conducted head counts at residence halls in an effort to account for everybody who may have been working on the structure. Some 60 to 70 students were believed to be on it when it fell.

Rusty Thompson, assistant director of the Memorial Student Center and the bonfire faculty adviser, said students told him "there was just a sudden movement. Five to seven seconds and it was on the ground."

Gov. George W. Bush choked up when he discussed the accident in a CNN interview. "I just can't imagine what that means to have that happen to them," he said. "It's sad, it's tough."

The bonfire tradition, which draws tens of thousands of spectators, began when Texas A&M was still an all-male military academy. The only year the bonfire was not lit was 1963, following President Kennedy's assassination.

This year's bonfire was scheduled for Thanksgiving night, the eve of the game. The event was canceled instead.

The large structure is built over the course of several weeks with multiple stacks of full-size logs put in place by cranes, tractors and students. The structure is designed to twist inward and collapse on itself as it burns.

The stack of logs would have reached 55 feet when completed; at the time of the collapse today, it was about 40 feet high.

Students who build the stack -- even cutting the logs themselves -- get safety training and get input from professional engineers, officials said.

Charles Hill of Crockett told WBAP-AM that his son, Caleb, was on the stack when it fell.

"He happened to be very fortunate. He has only a broken arm and a broken nose. He fell about 50 feet," Hill said. "Caleb is very emotional and very scared. Being part of the tradition, he feels a responsibility for those who have been injured. In a sense his family has been hurt."

Turner said many students think the tradition should be abolished. "I've spoken to quite a few who say it's not worth it," she said.

"Bonfire is one of most sacred traditions to Texas A&M's campus," Turner said. "It's one of the status symbols of our university. People say this is historic because this is the end of bonfire."

Bowen said he didn't know what will be done after this year.

"It's a very important tradition to us, but those decisions must be made at a calmer time," he said.

The project hasn't always been trouble-free: One stack collapsed in 1994, and a second was built and ignited.