CULIACAN, Mexico-- Sixteen men were shot dead and burned in two pickup trucks in the western city of Culiacan, officials said Wednesday, and seven other people were slain in the same state.

Neighbors called police after seeing a pickup truck on fire early Wednesday in the Antonio Rosales neighborhood of Culiacan, capital of the Pacific coast state of Sinaloa, said state Attorney General Marco Antonio Higuera Gomez.

Investigators found 12 bodies on the bed of the truck, some of them handcuffed and wearing bulletproof vests, Higuera said.

He said authorities are trying to determine if some of the victims are part of a group of nine people, including three local police officers, who were kidnapped in the town of Angostura on Monday.

Minutes after the first fire was reported, authorities received another call about a pickup truck burning behind a store. Police found four bodies inside that vehicle, and one had been decapitated.

Higuera said all 16 had been shot.

In two other almost simultaneous attacks hours later, four men were shot to death in the town of

Mocorito and another three in the town of Guamuchil, Higuera said. He said police are still investigating if the attacks are related.

Sinaloa, which is home of a major drug cartel named for the state, which has been fighting the Beltran Leyva drug cartel since it split off in 2008.