Prince George's County firemen were delayed momentarily in extinguishing a fire under a Metro subway car yesterday afternoon because a water line to the Landover Metro station platform was broken, officials said. No one was injured.

It is the second time in the subway's brief history that a fire-fighting water line has proved useless during an emergency.

The smoke under the last car of a New Carrollton-bound Orange Line train was reported at 1:28 p.m. The few passengers were evacuated and the Prince George's County Fire Department was called. When firemen arrived, they attempted to "charge" a dry water line located on the station platform. The line was broken.

Nancy Landes, spokesman for the fire department, said firemen switched immediately to an alternate water source and that there was almost no delay in the fire-fighting operation.

Metro has received criticism for its emergency preparedness in the last year, especially after a smoking trash fire in the long tunnel under the Potomac River last April. When Arlington County firemen reached the site of that small blaze, they had trouble getting water because the dry line was cracked. They, too, were able to find another source for water.

Yesterday's incident was a typical subway car fire: mostly smoke with little damage. Overheating in the brake system wiring caused the smoke, Metro officials said.