WARREN, Maine — One teen remains in critical condition while a second youth has been upgraded to stable condition after a Thursday morning crash that claimed the life of a Warren woman who a friend and family member called one of the most giving people she knew.

Knox County Sheriff Donna Dennison said the investigation into the crash continues and that, as part of that investigation, officers are checking to see where the people involved in the head-on collision were as far back as 24 hours earlier.

Alison Low, 38, of Warren died at the scene of the crash that occurred on Route 1 near Andes Variety shortly before 7:30 a.m. Thursday.

Police say that a 1997 GMC Sierra pickup truck driven by Samuel Simmons, 18, of Spruce Head was heading north on Route 1 when it crossed the centerline and struck head-on a southbound 2003 Subaru Forester driven by Low.

Dennison said investigators are still trying to determine what caused Simmons to cross the road. She said Simmons had been driving north from Bath.

Injured in the crash were Low’s two passengers — her son, Dustin Kimball, 18, of Warren, and her son’s girlfriend Olivia Blachet, 18, of Waldoboro. Both were taken to Maine Medical Center in Portland.

Blachet remained in critical condition Friday morning while Kimball was upgraded Friday from critical to stable condition.

District Attorney Geoffrey Rushlau went to the scene of the fatal crash, the sheriff said.

Breezy DuBay of Warren said Low was a kind person.

“She would give you the last shirt off her back,” DuBay said.

DuBay is the niece of Low’s husband, Darrin Low. DuBay said she would have coffee nearly every morning with Alison Low and they would talk on the phone for at least for a few minutes nearly every day.

Low was excited that she was soon to be a grandmother for the first time, DuBay said.

Low had worked at the Maine Smoke Shop in Rockland for the past nine months.

The store’s manager, Desiree Munro, said Low was a happy, friendly person.

“She could cheer up anyone. She had an awesome personality,” Munro said.