The accident happened about 7:15 this morning. The southbound highway remained closed until about 1 p.m. while the crash was investigated and cleared.
Christopher Vega, 20, of Plainville, was driving southbound on I-91 near exit 47E, when his car veered off the right side of the road. The car went onto the grass and then struck a tree, police said.
The three passengers who were in the car with Vega, were pronounced dead at the scene. The victims’ identities have not been released.
Vega was taken to St. Francis Hospital in Hartford for non-life threatening injuries.
On Saturday, a crash in Longmeadow, Massachusetts had 91 North closed in Enfield for about 10 hours.