Police Lt. Joaquin Kilson, a 19-year Police Department veteran, was fired Friday for his alleged association with a Fitchburg cocaine dealer.

A hearing officer appointed by the mayor ruled in favor of personnel charges against Lt. Kilson, including untruthfulness, improper associations and conduct unbecoming an officer, Sgt. Glenn Fossa said yesterday.

Lt. Kilson, 51, was placed on administrative leave in January, Sgt. Fossa said, after it was discovered he had associations with at least one of 16 people arrested Jan. 26 in “Operation Red Wolf,” a two-year investigation into illegal firearm sales, drug trafficking and related gang activities in Fitchburg.

Twenty people were indicted in Worcester Superior Court as a result of the investigation, including the 16 arrested that day. Sgt. Fossa said the cases are pending in Worcester Superior Court.

Lt. Kilson was questioned by the FBI and state and local police. An internal investigation, Sgt. Fossa said, determined he had regular social contact with a 37-year-old Fitchburg man indicted by a grand jury for selling cocaine during the two-year operation. He also maintained regular cellphone contact with the man and stayed at his home in the Dominican Republic, Sgt. Fossa said.

“We are saddened by this event, but must hold our officers to the highest standard,” Police Chief Robert A. DeMoura said in a news release yesterday. “The members of the department and our law enforcement partners cannot tolerate being in a position where their safety could be compromised. We are confident the department will heal and the community's confidence in the Police Department will continue.”

It was unclear whether criminal charges will be filed against Mr. Kilson.

Chief DeMoura would not say whether the full investigation is completed.

Mr. Kilson did not return phone calls seeking comment.