Four hours after Madison Wheeler said on Facebook that she was at a Folly Beach bar, authorities said the 20-year-old was driving about 82 mph on Johns Island.

Sheriff's deputies later suspected that she was intoxicated and using her cellphone early Sunday. When she reached a curve in Main Road, her rental car didn't turn left as it should have. The small sedan went straight, bounded off the road and hit a tree.

Wheeler was thrown from the car, and died at the scene.

The Charleston County Sheriff's Office on Monday was looking into factors suspected to have contributed to the fatal wreck, Maj. Eric Watson said. They included speed, the use of her phone and alcohol, according to a collision report.

Watson said it would be a while before investigators learn the results of toxicology tests on Wheeler's blood. The legal age for drinking alcohol is 21.

"That's normally part of an investigation if they have reason to think she was under the influence," Watson said. "We won't know for sure until we get the toxicology results back."

The report did not indicate a reason for deputies' suspicions. The collision report pointed to speed as the primary factor in the ensuing crash: about 32 mph over the limit of 50.

Around 3:15 a.m. Sunday, Wheeler was driving the Chevrolet southward on Main Road on Johns Island.

The bend in Main Road near Mary Ann Point Road is sharp, and Wheeler's car was going too fast to "safely negotiate" it, the report stated.

Reach Andrew Knapp at 937-5414 or twitter.com/offlede.