Two hikers became stranded Monday on a trail in Montgomery County, requiring help from rescuers, according to authorities.

The hikers reported that they set out on the rugged Billy Goat Trail in the C&O Canal National Historical Park about 6 p.m. but that it got dark before they could finish, the county fire and rescue service said.

The loop they were attempting to complete requires climbing and scrambling over steep and rocky terrain along the Potomac River, said Pete Piringer, spokesman for the Montgomery County Fire and Rescue Service.

A U.S. Park Police helicopter found the stranded hikers on rocks about 50 feet above the river, Piringer said.

Aided by light from the helicopter, rescue crews headed toward the pair, Piringer said. About 10:30 p.m., he said, the hikers and rescuers were making their way back over a distance of about a mile. No injuries were reported.