NASA's poor maintenance practices have caused a fire in a mission control room, falling concrete in a space shuttle building and a steam line explosion, according to a government report issued Monday.

The General Accounting Office report says the National Aeronautics and Space Administration is working to correct the shortcomings. Congress appropriated $141 million for maintenance in 1990, and more has been asked for future years.The GAO recommends that the space agency develop a comprehensive maintenance strategy, spend more money on upkeep and do annual surveys to determine which of its centers most need repairs.

"People and facilities are critical to mission success," said Sen. Barbara Mikulski, D-Md., who released a summary of the report Monday. "We can't afford breakdowns on the ground if we're going to have spectaculars in space."

The report said launch pads and the space shuttle processing facilities are generally well-maintained. But it said that eight NASA centers visited by GAO inspectors all have deteriorating facilities such as leaking roofs, peeling paint and leaking steam lines. Many of NASA's buildings are 30 to 50 years old.

The report said NASA rated its own facilities as marginal.