The Prince George's County fire department is investigating the use of a racial slur that was transmitted over the department's communications system this month, officials said yesterday.

Mark Brady, county fire department spokesman, said officials learned of the slur shortly after it was broadcast over the department's private frequency about 5 a.m. July 13. He said that the use of the "N-word" was recorded by a dispatcher because all transmissions are taped and that the transcript is central to the probe.

According to officials, someone said to "hold the [epithet deleted] from 42" after a dispatcher's request that all units except for Company 42 return from an Oxon Hill apartment fire. The incident was first reported Tuesday by WRC-4.

"We are very seriously investigating this incident and are working to identify the person responsible," Brady said yesterday.

The radio in question was used near Oxon Hill, but it was not a registered county radio, which has stymied the investigation, Brady said. The radio, he said, did not emit an identifier prior to the broadcast -- a violation of department orders and federal communications rules.

Every time firefighters speak into their radios, Brady said, an identifying number is also sent, and that number appears on computer screens at the county's Landover Hills communications center. Because no such number was sent July 13, Brady said, officials are investigating two possibilities: The epithet came from either a non-employee who hacked into the department's restricted frequency or a county employee using an unregistered radio.

If a member of the department is responsible, Brady said, punishment could range from suspension to dismissal. "If it's a civilian in the community, the most we can do is send the case to the Federal Communications Commission," he said.

To transmit on the county department's frequency, Brady said, a person must be authorized by fire officials and assigned an identifier. Other area jurisdictions, volunteer firefighters and paramedics and government agencies have that permission, he said.