Shortly before 8 a.m. on Friday morning, police say the bus was heading west on Port Tobacco Road in Nanjemoy, when for unknown reasons, the driver lost control and struck the dump truck, which was heading east, head-on.
Three occupants inside the bus - including the driver - were pronounced dead at the scene, according to state police. The driver and sole occupant of the dump truck was uninjured.
Investigators said that they do not believe that impairment was a factor in the crash.
The crash investigation led to lane closures on Port Tobacco Road between Bowie Road and Kimberly Place on Friday.
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