Thousands of school buses in Virginia are missing a device that prevents parking brakes from disengaging by accident.
State officials say up to 4,000 of the state's 17,000 school buses lack a brake interlock, The Richmond Times-Dispatch reports.
Officials noticed the missing device several weeks ago during a spot check. Several bus manufacturers have agreed to install brake interlocks on qualifying school buses for free.
The Virginia Department of Education said in news release that it was not aware of any crashes that had occurred because of the missing part.