An article in Friday's editions about Metro's problems with fare evasion and theft incorrectly stated that Metro police officers are issued keys to farecard vending machines. In fact, police officers are not issued such keys, Metro police chief Angus MacLean said.

Underpayment of fares, station burglaries and in-house thievery are costing Metro perhaps as much as $7 million a year or more, according to a staff study released yesterday.

"This is a loss of a magnitude that we can't live with," said Cleatus Barnett, chairman of the Metro board's internal affairs committee. The committee's members responded to the report with new calls for tougher enforcement of fare collection and more equipment to combat thefts and cheating.

The study estimates as much as $5 million a year may be lost to unintentional underpayment of fares, based on surveys asking riders to describe the rides they took and tell how much they paid. Officials said money is also lost through deliberate cheating on the buses or in the Metrorail system, but could not estimate how much.

Electronic records in farecard vending machines indicate employes with keys to machines stole $814,000 from them in the year ending last June 30, the report said. These same records, which Metro officials admit are not foolproof, indicate employes took another $319,000 between July and December.

Burglars using sledgehammers, crowbars and wirecutters broke into farecard machines and made off with $147,000 in the first 11 months of 1982, the report said. Repairing the damage they caused cost another $190,000. Undetermined sums of money also vanished from fareboxes of buses parked at Metro garages and from collection equipment at parking lots.

Since it began operations, Metro has fought a constant battle against fare evasion and theft. The report indicates that underpayment and theft now equal 4 percent of fare income or more, and cracking down has gained new importance as operating expenses and area governments' subsidy payments continue to rise rapidly.

The board panel, briefed on the problem yesterday by staff members, requested further study of antitheft and antievasion programs. "If people find out you can beat the system, it becomes an accepted practice," said board chairman Richard J. Castaldi.

The panel called on Metrobus officials to cut underpayment of fares in the bus system by whatever steps they choose. Much of the loss results because drivers do not know the correct fares and fail to check whether their riders pay them, Metro officials said.

Management and the drivers' unions have argued for years over whether fare enforcement is a driver's job. James M. Thomas, president of the Amalgamated Transit Union local at Metro, contends it is not, saying enforcement can lead to assaults on drivers and the filing of official complaints against them.

Transfers are now free. According to Metro, riders often give them away or sell them to other people, who then board buses without paying at all. A 5-cent charge for tranfers included in fare increases proposed for April is expected to cut down on the number of transfers being issued.

The panel ordered further study of efforts to combat rail fare evasion by improving faregate components that reject tainted cards and making attendants enforce fares more rigorously. Attendants are also receiving farecard "readers," electronic devices that can show where a suspect card entered the system and other information useful in combatting abuse.

To counter burglaries, Metro is currently designing a metal barrier to go around banks of farecard vending machines, with a heavy door that would be closed at night. The first is to be installed at the Stadium-Armory station. Last year, 29 people were arrested in connection with machine break-ins.

General Manager Richard S. Page told the panel Metro may have to replace the fareboxes now used in buses, which are frequently broken into.

Metro officials said nine Metro employes were arrested in the past year in connection with the theft of fare revenues, and two were charged with taking money collected at parking lots. One employe was caught with $2,626 in December, officials said, allegedly taken from farecard machines.

Reducing the number of farecard machine keys may be the best way to reduce thefts by employes, the report said. Station attendants, employes who service the machines and Metro police officers currently have keys.