DENVER, Feb. 6—Multiple explosions destroyed 24 empty school buses and damaged 15 more last night when at least 12 dynamite bombs went off under their as tanks.

School officials had no expla nation today for the massive and skillful demolition job, which caused $200,000 worth of damage. The buses were parked in a fenced school lot about two miles southwest of downtown Denver.

Four trucks were also de stroyed in the explosions and six other vehicles were dam aged.

Acting Fire Chief Daniel Cro nin said that the dynamite bombs had been tied together.

“The whole thing went up at once,” he said. “In my opinion, it was a strictly professional job.”

Three young white men were seen running from the area shortly before the explosions and are being sought by the police.