A woman riding on a mattress on top of a van in Prince William County fell off the vehicle to her death Friday, police said.

At around 6:40 a.m., officers responded to a report of a single-vehicle crash involving a 2006 Chevrolet Express van in the area of Bent Grass Drive and Waverly Farm Drive in Haymarket, Prince William County police said in a statement.

An investigation revealed that 20-year-old Sidney Zelaya Gonzalez of Culpeper was riding on an unsecured mattress on top of the van when the mattress came off, the statement said.

The driver of the van was a 41-year-old woman of Culpeper, according to the statement, but police did not provide her name. Speed and alcohol do not appear to be factors in the crash, police said, and charges may be filed against the driver, who remained at the scene.

Officer Nathan J. Probus, a spokesman for Prince William County police, said the accident was not the result of a “joyride,” but that the women were trying to transport the mattress, resulting in a “tragic situation.”

“It’s a bizarre case,” he said. “I don’t remember ever having to deal with a situation like this.”