BUFORD, Ga. (AP) — State authorities are investigating a boating accident at Lake Lanier that left one man dead and a woman seriously injured.

Gwinnett County firefighters responded to a report of a boating accident at the lake after a passing motorist called 911. According to authorities, a couple was crossing the lake in a 21-foot ski boat when they reportedly struck an unknown object in the water. The couple swam to shore to get help and was later treated at a local hospital for minor injuries.

Authorities were able to locate the second boat around 5 a.m. An adult female was found aboard the damaged vessel and transported to a nearby hospital in serious condition.

The state Department of Natural Resources and the U.S. Army Corps of Engineers are investigating the incident.