The fire is at the Milford Auto Recycling Co., at 70 S. Washington St. near Bridgeport Avenue, Milford police said via Twitter.
Police also urged drivers to avoid the area and seek alternative routes if possible.
"Traffic on the Post Road near Bridgeport Avenue is extremely heavy," police said. The fire began at about 3:30 p.m. and was still burning a couple of hours later.
Stratford Engine 1 and Engine 2 are assisting Milford with the large fire, Stratford fire officials said via Twitter.
No injuries have been reported in the smoky blaze, NBC Connecticut reported.
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