Mexico City (CNN) -- Authorities in the northern Mexican city of Torreon said Saturday that they found 10 "mutilated" bodies inside the back of a truck, the state-run news agency reported.
The seven men and three women appear to have been killed several days ago in various locations outside the city and then later brought in, Notimex reported.
The news agency said authorities also had reports of human heads, found throughout Torreon, but it was not immediately clear whether those heads belonged to the bodies in the truck.
Separately, gunmen entered a downtown bar in the northern Mexican city of Monterrey and shot 20 people dead, police told the state-run news agency Saturday.
A preliminary investigation suggests that attack was sparked by a dispute between organized crime groups for control of the El Sabino Gordo nightclub, where drugs are allegedly sold, said Jorge Domene Zambrano, a public safety spokesman.
"We know that an armed group came in two vehicles and went into the bar, made a series of shots ... 20 people died," he told the Notimex news agency. Five others were wounded and taken to the hospital.
Domene Zambrano said the attack late Friday night was likely the work of a rival gang. Many of the dead were employees of the nightclub, he said.
In a third incident, the bodies of 10 men and a woman were found Friday afternoon on the eastern outskirts of Mexico City, a Valle de Chalco municipal government official said in a statement.
The public security official, Javier Garcia, said the victims -- all of whom were in handcuffs and bound with tape -- had been shot.
Nationwide, there have been some 35,000 drug-related deaths since President Felipe Calderon began a crackdown on the cartels in December 2006, the Mexican government says.