WASHINGTON (AP) - Initial testing Friday found no anthrax in air samples and swabs from a Naval mail facility, but five employees were being offered antibiotics for possible exposure.

A service spokesman, Cmdr. Conrad Chun, said the Navy was awaiting further rounds of testing before reaching a definite conclusion.

A federal law enforcement official also said tests by late Friday had "come out negative" and further results were due Saturday afternoon.

Officials closed the Navy mail-sorting offices and 11 other post offices in and around Washington Thursday after an automated alarm and one follow-up test indicated the possible presence of anthrax spores at Anacostia Naval Station.