The crash is between Exits 15 and 14, DOT said.
As of 5 p.m., the traffic is congested for over 8 miles from Exit 19 down to Exit 14 because of the serious crash, DOT said.
The left and center lanes are closed as of 5 p.m., nearly two hours after the crash occurred, DOT said.
The Norwalk Fire Department extricated the driver of the coach bus along with passengers from the wreckage, according to The Hour.
The driver suffered serious injuries and was transported to Norwalk Hospital, according to The Hour. Several passengers on the bus, which was full, were also injured, State Police told The Hour.
It was not clear how long it would take to clear the scene. Two lanes remained blocked as rush-hour began.
Click here to follow Daily Voice Stamford and receive free news updates.