The search will continue Sunday for an Aspen Hill man who disappeared while swimming in the Triadelphia Reservoir in upper Montgomery County.

Authorities identified the man as Bruce Yansen, 21, who may have drowned Friday afternoon in the popular recreational spot in Brookeville near Route 97, according to the Washington Suburban Sanitary Commission.

The initial search was called off Friday because of darkness and continued for seven hours Saturday with help from the Howard and Montgomery county fire and rescue departments.

The reservoir is a popular destination for fishing and kayaking, but it is off-limits to swimmers because it is also used as a water supply.

Scott Graham, assistant chief of the Montgomery fire and rescue service, said Yansen and a friend were walking in a shallow section of the reservoir when they inadvertently dropped off an underwater ledge into an area 18-feet deep.

Neither of the young men were strong swimmers and they panicked, Graham said. The missing swimmer lost his grip on his friend’s arm and went under, Graham said.

“Although we have beautiful scenic water around us, it’s all very dangerous because of what we can’t see,” Graham said.

On Saturday, the WSSC closed Triadelphia Recreation Area and the Big Branch Recreation Area. All WSSC recreation areas had reopened by late afternoon and will remain open Sunday.