Mexico City, Feb 20 (IANS/EFE): The police chief of the Mexican border city of Nuevo Laredo is missing and two of his brothers have been murdered, prosecutors said.

Roberto Alejandro Balmori Garza's whereabouts is not known and orders have been given to find the municipal police chief, the Tamaulipas state Attorney General's Office said in a statement.

Prosecutors, however, did not say what theories investigators had about the police chief's disappearance.

The bodies of Manuel and Jose Alberto Balmori Garza, two of the police chief's brothers, were found Monday in a vehicle parked on the highway that links Monterrey and Nuevo Laredo.

The two men had been shot to death, officials said.

Manuel Balmori Garza was a federal Attorney General's Office agent.

Nuevo Laredo, a city of some 400,000 located across the Rio Grande from Laredo, Texas, is the third most violent city in Mexico after the Pacific resort of Acapulco and the north-central city of Torreon, a recent private report concluded.

Nuevo Laredo police chief Gen. Manuel Farfan Carriola, four bodyguards and an aide were gunned down in February 2011.

Farfan had served as Nuevo Laredo public safety secretary for just 33 days when he was killed.

He was one of nine former military officers hired to take over the command of police departments in Tamaulipas.

The Gulf and Los Zetas drug cartels have been fighting for control of Nuevo Laredo and smuggling routes into the United States.

After several years as the armed wing of the Gulf cartel, Los Zetas, originally a band of Mexican special forces deserters, went into the drug business on their own account and now control several lucrative territories.