The police chief of the violent Mexican border city of Nuevo Laredo is missing.
Tamaulipas state prosecutors said they have opened an investigation into the whereabouts of Roberto Balmori Garza, police chief of the city across the border from Laredo, Texas.
Local media reported that two of Mr Balmori Garza's brothers were found shot dead on Sunday inside the boot of a car in the neighbouring state of Nuevo Leon.
One of his brothers was a federal investigator, media reported.
Tamaulipas prosecutors' spokesman Ruben Dario said Mr Balmori Garza disappeared over the weekend.
He said he could not give any other information on the case or confirm the reports of the death of the police chief's brothers.
Nuevo Laredo, a stronghold of the Zetas drug cartel, has been the scene of bloody drug-gang turf battles since the beginning of the year.
Two years ago, gunmen killed a retired army general who had been police chief of Nuevo Laredo for a month. Two of his bodyguards were also killed and two were wounded.
The Zetas, known for its viciousness, has been fighting its former ally, the Gulf cartel, in Mexico's north-east since early 2010.