WHATELY — A 47-year-old man from Haverhill, New Hampshire, was killed Tuesday morning in a single-vehicle crash on Interstate 91 in Whately, according to the Northwestern District Attorney’s Office.

The man was the sole occupant of a tractor trailer that left the southbound lane, entered the median and crashed into trees. According to the DA’s office, the victim was pronounced dead at the scene by South County EMS.

The crash remains under investigation and the Office of the Chief Medical Examiner will determine the cause of death. State Police troopers assigned to the DA’s office, along with members of the State Police Collision Analysis and Reconstruction Section, the Crime Scene Services Section and the Commercial Vehicle Enforcement Section, responded.