CHESTERFIELD — A Chesterfield man died early Sunday morning after being critically injured when his snowmobile hit a tree.

Derek Graves, 37, was snowmobiling with a friend around 1:30 a.m. near Smith Road in Chesterfield. Graves’s friend, who was not far behind him, called 911 after coming upon the crash. Graves was taken to Cooley Dickinson Hospital in Northampton, where he succumbed to his injuries.

State Police detectives assigned to the Northwestern district attorney’s office, Chesterfield Police, State Police troopers from the Crime Scene Services Section and the Collision Analysis and Reconstruction Section, and the Massachusetts Environmental Police were at the scene of the crash. The accident remains under investigation, according to the DA’s office.

The Office of the Chief Medical Examiner will determine the cause of death.

Alexander MacDougall can be reached at amacdougall@gazettenet.com.