A 55-year-old woman was in serious condition after her motorcycle struck the side of a pickup truck in Sebago on Saturday.

The Cumberland County Sheriff’s Office said Amy Bacon of Windham was driving a 2007 Harley-Davidson motorcycle north on Route 114 at about 9:30 a.m. when it crashed into a truck driven by Lindsay Madison, 28, of Divide, Colorado.

Police said Madison was traveling south when she turned her truck left onto Shaw Road and did not see the oncoming motorcycle. The motorcycle hit the side of the truck, between the rear tire and back door.

Bacon was not wearing a helmet.

She was taken to Maine Medical Center in Portland by a medical helicopter where a spokeswoman listed her in serious condition Sunday night.

Madison and an infant passenger were taken to Bridgton Hospital for observation.

Police said speed and alcohol do not appear to be factors in the crash.

The accident remains under investigation.