The death of a 40-year-old Boston woman who fell from the upper deck of Tobin Bridge Tuesday night is thought to involve no foul play.

The woman, whose identity was not released, parked her car on the Tobin Bridge around 7:30 p.m. and went over the rail, landing on a Charlestown street below.

The preliminary investigation does not suggest foul play, the Suffolk County District Attorney’s office said.

Asked if the death is being treated as a suicide, a spokesman for that office said Wednesday, “It’s being treated as a non-homicide.”

State Police and the DA’s office continue to investigate the matter.