Authorities suspect boiler caused blast.

An explosion and fire erupted in the basement of a nursing home in Flint, Mich., on Nov. 10, blowing off a section of the roof and collapsing part of the building. Authorities initially suspected that one of the boilers could have exploded, but have since expanded the probe to look into other causes.

The blast killed five people - three residents of the home and two employees - and injured 32.

As investigators from state, federal and local agencies converged on the Clara Barton Convalescent Home, attention centered on the natural gas lines and the three boilers housed in the room where the explosion took place. Initial speculation centered on the boilers, but according to Flint fire officials, someone reported smelling gas sometime before the explosion.

At press time, it is still not known whether the natural gas fire that ensued was the cause or the result of the explosion.

Maura Campbell, a spokeswoman for the State of Michigan's Department of Consumer and Industry Services, which oversees nursing homes, indicated that the investigation could take months to complete.

Federal investigators from the National Transportation Safety Board, which investigates natural gas lines, have sent the gas meter, gas regulator and parts of the gas piping system to Washington, D.C., for analysis. Also garnering the attention of investigators are three natural-gas-powered clothes dryers and a natural-gas-fueled emergency generator housed in the same area of the basement.

The boilers in the 36-year-old building included two gas-fueled tube boilers, installed in 1986 and 1993, that provided domestic hot water for the home. A third boiler, a gas-fueled cast-iron boiler installed in 1963, provided heat for the building. The boilers are required by law to be inspected every two years. They were last inspected on Nov. 24, 1998, by the Hartford Steam Boiler Inspection and Insurance Co., and were not due for another inspection until November 2000.