Drugs and alcohol don't appear to be a factor in a boat accident in the Gulf of Mexico that left four people dead, authorities said Sunday.

Louisiana Department of Wildlife and Fisheries spokesman Adam Einck said a boat carrying five people took on water and capsized Saturday after leaving a marina near Venice.

Einck said Heath Dowsey, 33, of Alabama was the only survivor. Einck said three of those who died were from Alabama: Randy Dowsey, the survivor's father; Wayne Dowsey, the survivor's uncle; and a woman, Kerri Burns. Einck said officials had earlier misidentified Wayne Dowsey as the survivor's father and Randy Dowsey as the survivor's uncle.

Einck said Kenny Mock of Metairie, La., also died. The Coast Guard had initially said his last name was Mac, but Einck said the man's name appeared as "Mock" on his driver's license.

Investigators are working to find out if weather or wave conditions played a role in the accident, Einck said. Based on interviews with the survivor, officials believe the boat's engine quit before it began taking on water and overturned.

Einck has said Heath Dowsey told authorities he held onto a rope on the front of the capsized sport fishing vessel. Dowsey told investigators that the four others held on to the side of the boat and to four lifejackets before they became unresponsive, Einck said.

Authorities believe they died of hypothermia in the cold water.

The lone survivor was found by an oil industry supply vessel Friday afternoon and then was taken ashore, where he was treated for mild hypothermia.

The boat capsized about three miles offshore, near the South Pass entrance to the Mississippi River.