The Metro system has put more uniformed transit police on duty and stepped up its response to suspicious incidents since the Persian Gulf War broke out two weeks ago, officials said yesterday.

Metro police have handled more than two dozen calls to report potential problems since Jan. 15, but "there has been no credible threat" of a terrorist incident against the system, an official said.

The U.S.-led war has heightened fear of terrorism in this country, leading to a ban on curbside check-in at local airports, tougher identification checks at federal buildings and an increased police presence at buildings such as the Capitol deemed to be potential targets.

Although some Metro riders told reporters when the war broke out Jan. 16 that they would stop using public transit because of their fears of potential terrorism, Metro officials said yesterday ridership has not fallen.

William A. Boleyn, Metro's acting general manager, told the transit system board that the stepped-up security is designed to increase vigilance but not overly alarm employees or the public.

Metro has stationed about 5 percent more uniformed officers in public places, adding to its force by adjusting schedules and putting all transit police in uniform, officials said. The Metro system has about 375 officers, although about 40 percent normally are assigned to duties other than patrolling stations, trains and buses.

Metro operates 63 stations on 73 miles of track, 1,600 buses and bus and rail storage and maintenance facilities throughout its 1,489 square miles of service area.

Employees have been ordered to be on the lookout for abandoned packages, unattended vehicles or people acting suspiciously, Boleyn said.

The transit police have handled 27 calls since Jan. 15 reporting potential security threats, mainly reports of abandoned property, all of which turned out to be harmless, said Burton E. Morrow, Metro's acting chief of police. There have been no bomb threats against Metro stations or trains, officials said.

In one case, a bomb-sniffing dog was brought in to check an abandoned package that turned out to contain cookies, officials said. In another, the shopping area at the Pentagon received a bomb threat, resulting in the closing of the gate between the shops and the Pentagon Metro station, but the station itself was not closed.

Another suspicious package turned out to be a shoebox containing a pair of dirty sneakers.

Boleyn told the transit authority board that police are "even more vigilant" about checking employee identification and are in daily contact with local and national intelligence agencies about potential threats.