A prosecutor says the killing of a federal congressman last month in the southern state of Guerrero was ordered by a local mayor, but isn't revealing the official's name or motive.
Guerrero Attorney General Alberto Lopez says one police officer and another suspect have been detained in the case.
Lopez says one has confessed being paid to help kill congressman Moises Villanueva and his driver.
The two went missing Sept. 4 and their bodies were found about two weeks later in a river.
Legislators from Villanueva's Institutional Revolutionary Party had demanded that a state official be investigated for possible involvement in the killing, citing suspicions of a political motive.
Lopez announced the arrests Wednesday.