Rescuers spent four hours searching for a Potomac River kayaker on Friday — finding only a red kayak and a paddle — and were expected to return to the river Saturday to continue looking, officials said.

The kayaker was last seen about 2 p.m. in the Great Falls area northwest of Washington DC. Rescuers were hampered by high water levels, strong currents and debris in the water from heavy rains, said Pete Piringer, a spokesman for the Montgomery County Fire and Rescue Service.

As of 6:30 p.m., officials did know the identify the missing boater, who may have been kayaking alone. Rescuers were holding out hope that he may have made it to the shore, or that somehow the kayak and paddle that were located had originated from boaters who were not in distress and had lost the equipment from some location upstream. “No one saw him actually go into the water,” Piringer said.

About 2 p.m., a woman at an observation deck saw a man in his kayak struggling in the strong currents, Piringer said. She tried to call 911, but couldn’t get a signal, apparently because of the terrain around her. She made her way to a visitors’ center, where she called 911, Piringer said.

In quick order, at least six boats were in the water — carrying rescuers from Montgomery County, Md., on one side of the river and Fairfax County, Va., on the other side, Piringer said. A helicopter from the United States Park Police also joined the effort, as did rescue workers walking up and down both banks.

The rescuers walking the banks shouted, hoping to get a response from someone clinging to a rock or branch, but never got a response, Piringer said.

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