Rescue workers plan to resume their search early Thursday for a 19-year-old man who went underwater last evening while swimming in a cove in Triadelphia Lake, west of Clarksville, Md.

Montgomery County Fire and EMS spokesman Pete Piringer said authorities got a phone call around 6 p.m. Wednesday concerning a man who went missing in the water, near the boat ramp of Greenbridge Recreation Area. He was with friends who called for help. Swimming is prohibited in the area, though fishing and boating are okay.

Rescue workers have searched the shoreline with sonar and imaging technology. About a dozen boats were made available by Howard and Montgomery County fire departments, about four in the water at a time, until a heavy downpour and isolated thunderstorms forced them out of the water around 9 p.m. Wednesday.