BARTLETT, N.H. — A New Hampshire man who sought refuge on an island after his kayak overturned in the Saco River was located early Sunday thanks to a drone equipped with thermal sensors, officials said.

The drone operated by Center Conway Fire detected a heat source on an island, and the North Conway and Bartlett Fire Swift Water Rescue Team successfully located the man after midnight.

Mark Thompson, 69, of Conway, New Hampshire, was cold and wet but otherwise unharmed, officials said.

He and his son intended to paddle downstream but both capsized their kayaks Saturday afternoon.

His son was reunited with his kayak, but Thompson was separated from his kayak and had to swim to safety. He was last seen on shore around 2 p.m., officials said.