Concerns are being raised about heating buildings in downtown Ottawa following an explosion Monday that killed a 51-year-old man.

The boiler blast at the Cliff Street Heating Plant near Parliament puts several thousand government workers at risk of cold since that was the main facility for generating steam-based heat through downtown.

Special hazardous materials teams entered the building today to examine the explosion site; there are concerns about the insulating asbestos wrapped around the pipes in the facility, which may have broken free in the explosion.

Government department Public Works sent a memo to employees advising them to close windows and keep thermostats at 18 degrees in an effort to stave off the cold.

There is no word about when full service will be restored, and no one is yet sure about how the explosion occured.

"Our sympathies go out to the family of the gentleman who passed away and colleagues," says federal minister John Baird, who has a riding in Ottawa.

"It must be a very difficult day . . . we obviously want a full investigation to look at what happened."

The explosion left the unnamed worker with second-degree burns to 60 per cent of his body. He died in hospital on Tuesday, while two others were injured in the blast.

Another building is slated to take on the heating load as the boiler is examined and fixed.

Public Works is investigating the intregity of the building and the cause of the explosion.

With a report from CTV Ottawa's Norman Fetterley