PHILADELPHIA (CBS) – Water rescuers combed the Schuylkill River along Kelly Drive near the Girard Avenue Bridge on Friday after a witness observed a vehicle entering the river.

Overnight, rescue workers paddled down the river in a boat while Philadelphia police and firefighters shone spotlights on the water.

Later, as the first rays of sunlight illuminated the scene, an oil slick was visible on the water’s surface and at least one rescue boat was located near the area.

Anthony Manduzio, a man who said he was fishing in the river, saw a car fall into the water.

“First thing I do is start running. I could have been faster, I wish I could have done more,” Manduzio said. “It went into the water on the other side of the bridge, drifted into the middle, drifted all the way to our side and then crashed headfirst to where the boat is right there.”

Manduzio said he called 911 and spoke to emergency dispatch.

Manduzio said a woman was driving the car, but the windows were tinted and he could not see if anyone else was in the car.

It is unclear when the vehicle will be found.

Due to the investigation, delays are expected on Kelly Drive near the Girard Avenue Bridge. Kelly Drive is reopened after a previous closure.

At about 6:30 a.m., divers were preparing to board a Philadelphia Police Department Marine Unit boat, presumably to conduct another dive.

This is a developing story and will be updated.