11/07/2012 BOSTON, MA Hazmat crews work to clean up Congress Street (cq) near Faneuil Hall (cq) in Boston after a pipe with asbestos burst. (Aram Boghosian for The Boston Globe)
Hazardous materials crews worked to clean up Congress Street near Faneuil Hall.
Aram Boghosian/Globe Staff

An underground steam pipe near Boston City Hall ruptured early this morning, spewing steam and a small amount of asbestos into the air, according to the Boston Fire Department.

The leak happened just after 1 a.m. on Congress Street at Hanover Street, said department spokesman Steve MacDonald.

When the 14-inch pipe ruptured, it sent steam and particles of asbestos insulation into the air, MacDonald said.

Advertisement - Continue Reading Below

“We’re not exactly certain yet as to what the cause is,” said Rowan Sanders, spokesman for Veolia Energy, the steam utility that operates the pipe. “It’s a rare episode.”

Steam was forced through the pipe, which is buried underground below a layer of concrete, and up through the road, creating “a mess in the streets,” Sanders said.

Utility officials hired a cleanup company to deal with the asbestos, which is sprinkled throughout heaps of broken concrete and dirt, Sanders said.

He said asbestos was a common form of insulation, but that crews will replace it with mineral wool once they gain access to the pipe.

“We have to clean it up and have it hauled away by licensed professionals,” Sanders said. “We have to clean all the physical dust that we see and make sure that’s disposed of safely.”

The steam utility covered the leak with a temporary plate and plans to dig up the street and fully repair the pipe once an exact time can be set up with city officials, he said. Part of Congress Street was closed for the cleanup; it was reopened by Wednesday afternoon.

“We’re doing continuous testing to make sure the public is safe,” Sanders said. “The air tests all came back clear.”

The burst pipe did not cause any injuries or service interruptions to customers, but the company hopes to determine the cause to prevent it from happening again, he said.

“You really have to study the root cause so you can figure out what’s happening and how you can prevent it,” Sanders said. “We apologize for any inconvenience to any vehicular or pedestrian traffic.”