Seven municipal police officers were arrested in connection with the kidnapping, torture and murder of a marine in the eastern state of Veracruz, the Mexican Navy Secretariat said.
Three marines were abducted, tortured and murdered recently, with two of the killings occurring in Veracruz and one in the northwestern state of Sinaloa, the secretariat said last week.
The three unidentified marines were involved in operations targeting drug traffickers and other criminal organizations.
The police officers were arrested in connection with the killing of a marine whose body was found on June 11 near the Tuxpan River in Veracruz, the secretariat said.
The navy has participated actively in the war on drugs, with marines involved in the December 2009 killing of drug lord Arturo Beltran Leyva.
Gunmen later murdered several relatives of marine Melquisedet Angulo Cordova, who died in the shootout in which Beltran Leyva was killed on Dec. 16, 2009, in Cuernavaca, the capital of Morelos state.
The gunmen, all suspected of being members of the Los Zetas drug cartel, killed Angulo Cordova's mother, two brothers and aunt.
The marine's relatives were murdered on Dec. 21, 2009, at the family's home in Paraiso, Tabasco, just hours after their loved one was laid to rest with full military honors.
A total of 15,270 people died in drug-related violence in Mexico last year, and nearly 40,000 people have died since President Felipe Calderón declared war on the country's cartels shortly after taking office in December 2006.
Calderón has deployed tens of thousands of soldiers and Federal Police officers across the country to combat drug cartels and other criminal organizations.
The anti-drug operation, however, has failed to put a dent in the violence due, according to experts, to drug cartels' ability to buy off the police and even high-ranking officials.