A fourth person died Thursday from injuries sustained in a string of related accidents Sunday on Interstate 95 in the Waterford area, police confirmed on Friday.

Saumya Arora, 33, a dentist from Massachusetts, was pronounced dead at Yale New Haven Hospital where she had been listed in critical condition since the crash, according to state police.

Arora was a passenger in one of seven vehicles involved in a 9:26 p.m. crash on the southbound side of the highway near Exit 82. State police said a tractor-trailer carrying frozen food, driven by Kevin Custer, 60, of Swansea, Mass., struck three cars which in turn struck three more.

The crash occurred in an area of the highway that was congested because of several previous accidents, including a 7 p.m. crash in which another tractor-trailer had struck vehicles in the area of Exit 81.

Three people, including 2-year-old Dacari Robinson, his 9-year-old sister, Sanaa, and Dacari’s father, Darin Robinson, 26, perished in that crash. The children’s mother, 25-year-old Baughnita Leary of Meriden, was the sole survivor. A vigil was held Friday night for those three victims.

State police said the tractor-trailer involved in that crash was registered to Gold Medal Bakery and was driven by 58-year-old Gerard S. Dube of Swansea, Mass.

The accident was preceded by a multi-vehicle crash in Old Lyme.

Together, the crashes involved 16 vehicles and injured more than 20 people.

Police have not yet indicated whether the drivers of the two tractor-trailers would face criminal charges. The accidents remain under investigation.