The bodies of 16 people, including a prison official, were found in the past few hours in Durango city, the capital of the like-named northern Mexican state, prosecutors said Thursday.

Eight of the bodies were discovered in clandestine graves and the other eight, all of them headless, were found on city streets, the Durango state Attorney General's Office said.

Six "completely naked, decapitated" bodies were found at 5:30 a.m., with the six heads placed next to the corpses, the AG's office said.

"Two dead bodies, also decapitated," were found an hour later, but only one head was left with the bodies, prosecutors said.

"A wall with a 'narcomessage' on it" was spotted nearby, and the missing head, which belonged to deputy prison warden Gerardo Galindo Meza, was found on the ground under the message, the AG's office said.

Eight other bodies were found at a site in Durango city where army troops have exhumed 196 bodies in the past few weeks, state Public Safety Secretariat spokesmen told Efe.

The majority of the victims may have died in "settlings of scores" and kidnappings by drug traffickers, Durango Gov. Jorge Herrera Caldera said Wednesday.

The mass graves contain bodies from "confrontations between organized crime groups," Herrera said.

Four mass graves have been found since early April, but federal officials have provided few details about the killings.

The clandestine graves were found on April 4 at two sites in Durango city, with the majority of the bodies discovered in the state capital's Las Fuentes neighborhood.

The Sinaloa cartel, Mexico's oldest and largest drug trafficking organization, has been trying to gain control of Durango, the press reported.

Durango, one of the states most affected by drug-related violence, is reported to be the hiding place of Sinaloa cartel boss Joaquin "El Chapo" (Shorty) Guzman.

State and federal officials plan to start working in the next few days on a joint effort to identify the victims, the governor said.

The clandestine graves in Durango have now yielded more bodies than the mass graves in San Fernando, a city in the northeastern state of Tamaulipas, where 183 bodies have been unearthed.

The bodies found in the mass graves in Tamaulipas are believed to be those of people who were kidnapped by the Zetas drug cartel while traveling through San Fernando on buses and were later murdered.

The mass graves were found in the wake of reports that gunmen had forced men off buses headed for Reynosa, located across the border from McAllen, Texas, between March 19 and March 31.

Some gangs have resorted to using unusual methods to recruit gunmen because of the high casualties in the war being waged by rival drug traffickers for control of territory, the federal government says.

The incidents involving the buses may have been an attempt to recruit gunmen, investigators said.

The Sinaloa, Los Zetas and Beltran Leyva drug cartels may have been behind the killings in Durango, the press reported.

Nearly 40,000 people have died since President Felipe Calderon declared war on Mexico's drug cartels shortly after taking office in December 2006.