PHILADELPHIA (CBS) — Police are trying to determine how a car pulled from the Schuylkill River overnight ended up in the water.

The vehicle was discovered fully submerged in the water just before 3 a.m. Sunday along the 1800 block of Kelly Drive, near Boathouse Row.

Marine units removed the car from the river, but found no one inside the vehicle.

Police are working to figure out exactly what happened.