The crash was reported at about 3:50 a.m. on the eastbound deck of the bridge near Treasure Island, CHP Officer Herman Quon said.
Witnesses reported a Volvo speeding in one of the right lanes, Quon said. He said there were reports that the car was going more than 100 mph, but that those reports have not yet been substantiated.
The Volvo crashed into the rear of a 2007 Peterbilt truck, which was carrying recyclables and going about 40 mph. The Volvo became wedged underneath the truck and caught fire.
The woman driving the Volvo was pronounced dead at the scene, Quon said. Investigators are working to determine if she died of trauma from the crash or from the fire, he said.
The identity of the victim, a San Francisco resident, has not been released.
The driver of the truck, a Concord man, was uninjured.
The crash caused the closure of multiple eastbound lanes for more than two hours. All lanes were reopened by 6 a.m., Quon said.