Two firemen were injured and rush-hour traffic was disrupted yesterday evening by a fire that caused minor damage to upper stories of Old Post Office building on Pennsylvania Avenue NW.

About 50 firefighters responded to the scene of the fire, which started in the south central portion of the ninth-floor attic and spread to the two floors below. No damage estimate was available last night.

Deputy Fire cHief Dennis Logan said firefighters were hampered by a lack of an operational standpipe inside the building, having to carry hoses and equipment up to the attic after entering the building by ladder on the fifth floor. He said, however, that the small but smoky blaze was brought under control within 40 minutes.

Traffic was disrupted until 8:30 p.m. as police barricaded 12th Street between Pennsylvania and Constitution Avenues NW.

The gray, granite romanesque revival structure, which is included in the National Registry of Historic Places, was built in 1899. It is currently vacant and undergoing renovation for use as an office building and tourist attraction.

The two firefighters were treated for minor injuries and released from Washington Hospital Center. They were identified as Lt. John McCall and Sgt. Wallace Gooding.