A substantial amount of money, perhaps as much as $225,000 has been stolen from Metro's Farecard vending machines during a series of break-ins over the past 16 months, top Metro officials confirmed yesterday.

The break-ins, usually coming late at night after Metro's stations are closed, have resulted in an intensified campaign by Metro police to stem the problem. Thirteen people have been arrested in recent weeks in connection with the incidents, according to Metro General Manager Richard S. Page. In one incident early last Friday morning, a Metro policemen fired his revolver at a suspected burglar, but missed.

"We think the loss [of money] is considerable and we're concerned about it," Page said. He did not challenge the $225,000 estimated loss figure, which was provided The Washington Post by another source.

Page said the burglary problem is just one of many questions he has about the cost effectiveness of the Farecard system, a fully automated ticket-selling and fare-collecting arrangement that has had major problems since it was introduced in 1977.

In addition to losses because of burglaries and break-ins, many schemes have been devised by Metro riders to evade or reduce the fare they are supposed to pay.

"Any fare system has a certain amount of loss," Page said. "We're trying to find out what the experience has been in other places and see how we compare. But if we're losing more than 1 percent of fares collected to all of these problems combined, I would be concerned."

Assuming Metro collects subway fares at the same rate for the rest of the fiscal year that it did for the first half, 1 percent of all fares would be $408,240.

A number of modifications have been made to the Farecard equipment by its manufacturer, Cubic Western Data. Those modifications combined with an intensified maintenance program, have substantially improved the system's reliability in recent months.

Further modifications are being made to the vending machines to make them more difficult to pry open, Page said. Damage to machines along has totalled $37,000 this year, Page said.

The shooting incident occurred at the Stadium-Armory subway station last Friday morning. Two Metro policemen on patrol after the station was closed, came upon a man trying to pry open a vending machine.

According to Metro Police Chief Angus B. MacLean, the man came at the policemen with a crowbar when he was ordered to surrender. One of the policemen, Sgt. Gilberto Dowling, fired his revolver once, but missed. The man fled up the stairs but was captured outside a few moments later, MacLean said.

The man arrested was identified by MacLean as Duane F. Labaumbard, 33, of Southeast Washington. He was charged with burglary and assault on a police officer, MacLean said.

Both MacLean and Page said that after-hours security efforts have been intensified at Metro stations.