The right and center lane remained closed but were expected to reopen by about 1 p.m., DOT said.
The tractor-trailer fire was between Exits 15 and 14, near the junction with Route 7, DOT said.
Backups of about 9 miles to Exit 19 were reported on southbound I-95. Northbound I-95 was also congested in the area of Exits 11 to 14 in Darien and Norwalk.
Original story: NORWALK, Conn. -- Southbound Interstate 95 is closed in Norwalk due to a tractor-trailer accident, said the Connecticut Department of Transportation.
The accident was reported at 11:32 a.m. Thursday.
At least one truck is on fire between Exits 15 and 14. Traffic congestion is reported for 10.5 miles back to Exit 22.
The ramp from southbound Route 7 to southbound I-95 is also closed.
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