Propane 'vapor cloud' caused March explosion at school bus facility

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Sep. 1—Fire investigators say propane vapor ignited by an undetermined source caused the explosion that injured two employees at a Bradford school bus facility last winter.

The explosion and five-alarm fire occurred at the Student Transportation of America facility on Route 114 on March 3.

In a news release from the state Fire Marshal's office, officials said a propane vapor cloud was released from one of the propane-powered school buses that the mechanics were working on that day. "The propane vapors were ignited by an undetermined ignition source, which caused the explosion and fire," officials said.

Investigators found "several mechanical and electrical ignition sources" inside the building that could have caused the explosion but the exact source could not be identified, the news release said.

Officials said the cause appears to be accidental and there is no indication of criminal activity.

The mechanics, who suffered serious injuries, had to be flown to Boston hospitals. The two are still recovering at home, the news release said.

Officials are asking anyone with information about this incident to contact the state fire marshal's office at 603-223-4289 or by email at