The westbound highway was completely closed earlier Wednesday, the Connecticut Department of Transportation said, but one lane was able to be reopened just after 6 a.m. and all lanes were reopened later.
The shoulder remains blocked by the accident during morning rush hour, DOT said.
The accident occurred between Exits 6 and 5, DOT said. Traffic is congested for about 10 miles back to Exit 10 in Newtown because of the crash, which was reported at 5:17 a.m., DOT said.
No injuries, and cleanup on the highway may last until mid-morning before all lanes will be reopened, state police said.
Motorists should expect delays in the area and seek an alternate route.
It was raining early Wednesday in the area, after periods of overnight snow, which could be causing slick road conditions in the area, DOT said.
Click here to follow Daily Voice Danbury and receive free news updates.