A police officer and an alleged drug cartel member were arrested in connection with execution-style killing of 24 men outside Mexico City, a federal official said Thursday.

Antonio Ramirez Cervantes, a municipal police commander in the town of Huixquilucan, allegedly kidnapped the victims and took them to the place were they were shot, said Marisela Morales, the head of the organized crime division of the federal Attorney General's office.

Alleged Sinaloa drug cartel member Raul Villa Ortega is accused of gunning down all 24 men.

The two men were arrested Wednesday night in Huixquilucan, near the capital, and were presented to reporters on Thursday. They gave their names but made no other comment. It was unclear if lawyers had been assigned to them.

The 24 bodies were found bound with duct tape and shot in the head on Sept. 12 in a rural area outside Mexico City.

Authorities believe the killings stemmed from a dispute over drug dealing territory. Attorney General Eduardo Medina has said at least 17 of the victims have been identified as bricklayers recruited into drug dealing.

It was one of the bloodiest massacres in the wave of drug violence sweeping Mexico. Fighting between drug cartels has become increasingly brutal, with bodies regularly turning up in public, often beheaded.

In the border city of Tijuana, a shootout Wednesday night left one soldier and four gunmen dead.

The fighting erupted when gunmen guarding a house opened fire on approaching soldiers, according to an army official who was not authorized to give his name. He said soldiers later found a body in a freezer inside the residence and 10 guns. Three men were detained.

Another shootout in Mexico City left two gunmen dead and five people wounded Wednesday night. That gunfight started when armed men hurled a grenade at police trying to arrest them, according to the city Public Safety Department. The grenade did not explode.

Government officials acknowledge that homicides have surged across the country this year, but have not regularly released figures. News reports indicate more than 3,000 people have been killed so far in 2008.

On Thursday, a group of kindergartners found a loaded gun during recess in their school in the southern city of Morelia, said state police director Mario Bautista. The children turned the gun over to their teacher, who notified authorities.