One Metro worker will be suspended without pay for a day and two others will get letters of reprimand for ignoring two alarms Wednesday morning that indicated fire sprinklers were filling the Mount Vernon Square Station with water, transit executives said yesterday.

An investigation revealed that lights flashed and a shrill noise sounded inside the operations control center at Metro's downtown headquarters at 1:03 a.m. A Metro worker shut off the alarm at 1:18 a.m. but did not tell anyone that something was amiss in the station, said Steven A. Feil, chief operating officer for rail.

A second alarm flashed a minute later and kept flashing on a computer in the downtown headquarters until after 8 a.m. but was also ignored, Feil said.

Metro officials said that it was unclear why no one noticed the second alarm and that eventually it was "scrolled over" by subsequent messages and indicators. Alarms and indicators frequently signal inside the operations control center as night maintenance crews shut down sections of the railroad to make repairs.

Every time a certain door is opened, for example, an indicator lights up in the operations center to alert supervisors. Between midnight and 2 a.m. Wednesday, 215 alarms or indicators flashed in the control center -- typical for that period.

But a sprinkler alarm carries more urgency because it indicates fire, Metro officials said.

"Why a person chose to ignore an indicator light that the sprinkler system was on, I have no idea," Metro board Chairman Robert J. Smith said. "As an architect, I know what a sprinkler means. Now, at that hour of the day, we didn't have to worry about many people being in the station. But still, it's a property problem. Let a sprinkler run for three hours, and you can have property loss."

The sprinklers, located behind the escalators that run between the street and the mezzanine, sent water gushing into the station for more than four hours until the station manager arrived to open the station and called for a plumber after discovering ankle-deep water on the mezzanine. The station did not open until 7:15 a.m.; it took maintenance workers two hours to mop up the water.

Metro managers said yesterday that they do not know why the sprinklers activated but suspect that they were triggered by electrical work conducted by Metro power crews. A Metro crew was inside the station to switch the electric load from one feeder to another in response to a request by Pepco, Feil said.

The operations control center is often referred to as the brain of the subway. It is staffed with controllers and supervisors who track every movement on the rail lines and are supposed to react to emergencies and ensure the safe operations of the trains and stations.

The operations control center has been criticized for mismanaging late-night subway service after the Oct. 10 Redskins game. Train controllers opted to run just one train an hour on several lines, inconveniencing thousands of football fans who sat on idling trains as night turned to morning.

As a result of that case, two Metro controllers will be suspended for three days without pay and a third will be suspended for five days without pay, Deputy General Manager James Gallagher said.