BRUNSWICK — Two motorcycle riders, who witnesses said were traveling at a high rate of speed, crashed their bikes on Harpswell Road on Wednesday afternoon, sending one of the riders to Maine Medical Center in Portland with serious injuries.

Brunswick Police Lt. Thomas Garrepy said 30-year-old Nathan Kane of Harpswell was taken to the hospital for treatment of a head injury. Kane was listed in critical condition late Wednesday.

The second motorcyclist, 22-year-old Joshua Kane of Harpwell, did not require medical attention.

Witnesses told police that Nathan Kane was traveling at a high rate of speed and closing in on a line of traffic when he lost control and slid to a stop in the vicinity of the Brunswick Town Commons, a town-owned park off Harpswell Road, which is also known as Route 123.

Joshua Kane tried to avoid a collision with other motorists and crossed both lanes of traffic before riding onto the shoulder of the road. He then continued north on Harpswell Road before losing control and sliding to a stop.

The crash remains under investigation by Brunswick police. It is not known if the riders were wearing helmets.