HARVARD (CBS) — One man is dead after a rollover crash on Route 495 south in Harvard overnight.

Massachusetts State Police responded to the crash scene, which was south of Exit 28, around 12:15 a.m. Tuesday. Preliminary investigations show that a man driving a 2005 GMC Sierra drifted from the left lane, struck the guardrail running down the median, and rolled over.

The driver was pronounced dead at the scene. He was the only person involved.

Speed is being investigated as a possible factor in the crash.

Police have not released an identity of the man.