An underground 14-inch steam pipe ruptured close to Boston City Hall this morning, releasing steam as well as low levels of asbestos fibers into the surroundings, the fire department in Boston informed. The leak occurred just after 1 AM on Congress St at Hanover St, department spokesperson Steve MacDonald said. When the pipe busted, it released steam and asbestos particles into the surroundings, MacDonald said. Asbestos had been used for insulating the pipe. â??We are not very sure yet what exactly caused the rupture. It is a very rare episode,â? Rowan Sanders, the spokesperson representing Veolia Energy, said in a statement. Veolia Energy is the steam utility, which operates the pipeline. Steam was pushed through the busted pipe that is buried beneath the ground under a concrete layer. The incident created confusion in the streets, said Sanders. Utility officials have hired an abatement company for dealing with asbestos that is sprayed all through the heaps of ruptured concrete and dirt, said Sanders He said asbestos material was a commonly used material, and it was especially used for insulating purpose. He said crews are going to replace the dangerous material with mineral wool when they get access to that pipe. â??We must clean up the asbestos and have the material hauled away by authorized professionals. Weâ??ve to clean up all the dust that can be seen and ensure that it is safely disposed of,â? Sanders said. The leak was covered by the steam utility with a provisional plate. Plans for digging up the street and completely repair that pipe once a specific time could be fixed with the city officials, Sanders said. A portion of Congress St has been shut for cleanup works. It will be reopened shortly. â??We are doing regular testing for ensuring that the public is absolutely safe. The air quality tests came back okay,â? Sanders said. If asbestos fibers are breathed in, it can cause fatal diseases including cancer. The broken pipe didnâ??t cause any serious injuries or service disruptions to the customers. However, the company expects to find out the reason for preventing it from occurring again â??You have to study the actual cause of the incident so that you will be able to figure out what is taking place and how can you prevent it. We regret any inconvenience caused to any pedestrian or vehicular traffic,â? Sanders said.