UPDATED Wednesday, Nov. 16, 1 p.m.

A Tewksbury man was involved in a fatal, head-on collision in Ayer early Tuesday (Nov. 15) morning.

According to Ayer Police, the accident occurred on Littleton Road (Route 2A) at around 5:45 a.m. The crash involved a box-style delivery truck and a Toyota Prius.

The driver of the Prius, identified as 67-year-old Claire Boudreau of Ayer, was pronounced dead at the scene. She was the sole occupant of the Prius, according to police.

According to Ayer Police, the preliminary investigation into the cause of the crash shows that the delivery truck was travelling westbound on Littleton Road, crossed the center line and hit the Prius head-on.

According to a spokesman for the office of Middlesex County District Attorney Gerry Leone, the investigation into the cause of the crash is ongoing. Because of the fact that no charges have been filed in the case, the driver of the delivery truck has only been identified as a 21-year-old man from _Tewksbury._

The man was taken by ambulance to Nashoba Valley Medical Center in Ayer for treatment of unspecified injuries.  The driver was the sole occupant of the truck.

The Middlesex District Attorney's Office, The Massachusetts State Police Accident Reconstruction Unit and The Massachusetts State Police Commercial Vehicle Enforcement Unit are assisting the Ayer Police Department with investigation.

Tewksbury Patch will continue to update this story as more information becomes available.