Florence County coroner Keith Von Lutcken said he sent the body of Victoria Carter Redden, 51, of Lake City down to the Medical University of South Carolina (MUSC) for an autopsy.
Redden's car ran off Knollwood Road and plunged into Forest Lake last Sunday afternoon.
Firefighters and two good samaritans rescued Redden from a completely submerged car.
Officials said it took crews 14 minutes to get her out of the car which was in about 15 to 20 feet of water. She was the only person inside of the car.
Drivers in the area at the time said Redden was not speeding before the crash.
It appears a medical condition may have contributed to the crash so tests are being performed, according to Lutcken.
Lutcken added that he wants to be 100% sure that it was a medical condition that led to the crash and that's why he decided to have an autopsy performed on Redden's body.
Initially, he was only going to have toxicology tests done.
Lutcken expects autopsy results to be in sometime Friday afternoon.