Police say eight workers have been injured in an explosion at a middle school in southeastern Virginia.

Newport News Police spokesman Lou Thurston says the workers suffered varying injuries in Sunday morning's blast at Crittenden Middle School.

They were employees of T.R. Driscoll Inc. of Lumberton, N.C., a contracting company that had been doing repair work at the school for about five weeks.

The cause of the blast is being investigated. Thurston says workers were using propane to heat the tar but no cause has been determined.

Five workers were taken to nearby trauma centers, and three to emergency rooms.

Thurston says the explosion sparked a fire and caused a large wall to collapse in the school's shop area. Monday classes were canceled.