BOSTON (WHDH) -- An overnight steam pipe break on Union Street released asbestos into the air creating a hazmat situation.

Boston Fire Department responded shortly after 1 a.m. to Congress Street at Hanover Street for an underground steam leak.

The explosion closed the Haymarket T stop and parts of Congress Street early Wednesday morning.

Traffic was detoured with delays expected.

The Haymarket T was reopened, but Congress Street between Sudbury and North Streets remained shut down for the morning commute. A section of Union Street was also closed.

Boston Fire Department handled the hazmat situation.

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