A mother was killed and her toddler son was critically injured when they were hit by a tractor trailer on Interstate 95 in Lincoln on Thursday, police said.

The woman’s car was parked in the breakdown lane and she was holding her son and was in the travel lane when they were hit around 4:30 p.m., Maine Department of Public Safety spokesman Steve McCausland said. He said the woman, who was in her late 20s, was killed instantly.

The boy was taken to Eastern Maine Medical Center in Bangor with severe injuries. The boy’s father is from a nearby town and was notified and went to the hospital to be with his son.

The circumstances of the accident remain under investigation and the names of the woman and the truck driver won’t be released until Friday, McCausland said.

The accident happened on I-95 about four miles north of Lincoln. State troopers closed the northbound lanes of the highway, detouring traffic at the Lincoln exit, while they investigated the crash.

Dennis Hoey can be contacted at 791-6365 or at:

dhoey@pressherald.com