Federal authorities have arrested a District police officer in an alleged conspiracy to use altered cellular telephones that became an integral part of a cocaine trafficking network operating in Northern Virginia.

The Secret Service alleges that Sergio Bonilla, 25, a two-year member of the District force, associated with known drug dealers who sought to gain access to the cellular phone network and make unlimited numbers of unbillable calls.

Bonilla's arrest Thursday night was part of an investigation initiated after Washington area cellular phone company representatives told Secret Service agents that they were experiencing fraud.

He was charged with knowing use of one or more counterfeit access devices with the intent to defraud. If convicted he faces up to 15 years in prison and a $100,000 fine. U.S. Magistrate W. Harris Grimsley ordered Bonilla held without bond yesterday and scheduled a Jan. 29 preliminary hearing.

According to an affidavit on file in U.S. District Court in Alexandria, alleged drug dealers had obtained cellular phones programmed with counterfeit computer chips. Hundreds of calls were made from the altered telephones, the affidavit said.

In October, Drug Enforcement Administration agents confiscated an altered telephone and several kilograms of cocaine, $37,000, scales and a submachine gun when executing a search warrant at an Arlington apartment in the 2100 block of Jefferson Davis Highway.

Two months later, as the investigation continued, the Secret Service interviewed Romulo Deleon, an alleged member of the drug trafficking group who identified members of his organization and told how cellular phones were used in the operation, according to the affidavit.

Cellular phones, law enforcement officials said, have become popular with some drug dealers who are afraid of having their home phones tapped or who fear that they might be shot at while using public telephones.

Deleon told police that he and Bonilla lived in the same Arlington apartment complex and that Bonilla "was friends with several members of the drug dealing organization and knew its members were selling drugs," the court documents said.

Deleon also told the Secret Service he personally discussed with Bonilla the capacity of a certain type of phone, when altered, to make unbillable calls.

In addition, Deleon claims that Bonilla often came to Deleon's apartment to make unbillable calls.

Bonilla, who was a patrolman in Washington's 4th District, had been placed on paid administrative leave on Aug. 21, 1990, pending an unrelated investigation, D.C. police said.

His police powers were revoked.

Staff writer Gabriel Escobar contributed to this report.