WARREN, Maine — The 18-year-old driver whose pickup truck crossed the center line and struck a car head-on, killing its driver and critically injuring a passenger, has no recollection of the crash, according to police.

Knox County Sheriff’s Office Chief Deputy Tim Carroll said investigators also have determined that texting did not play a role in the crash. The case remains under investigation, he said, and no reason yet has been found for why the vehicle crossed the line.

The sheriff’s office has said the 1997 GMC Sierra pickup truck driven by Samuel Simmons of Spruce Head was heading north on Route 1 shortly before 7:30 a.m. Thursday, when his vehicle crossed the center line near the intersection of Western Road and struck a southbound 2003 Subaru Forester driven by Alison Low, 38, of Warren.

Low died at the scene of the crash. Her 18-year-old son, Dustin Kimball of Warren, was seriously injured. His condition was upgraded, and he was discharged Friday from Maine Medical Center in Portland. His girlfriend, Olivia Blachet, 18, of Waldoboro, remained in critical condition Monday at the Portland hospital.

Drug and alcohol tests were also done as part of the investigation, but those results have not been come back yet, Carroll said.