The announcement from state officials marked the latest gruesome news involving mass graves in areas hit by rampant drug-related violence.

Officials said the total probably includes 122 passengers from a bus that was commandeered near the town of San Fernando, some 160 kilometers (100 miles) from the US border.

San Fernando was the same municipality where the Zetas drug cartel last year kidnapped and slaughtered 73 immigrants from Central and South America on their way north to try to illegally cross into the United States.

Tamaulipas state has suffered an explosion of violence for more than a year blamed on battles between the Zetas -- a gang formed in the 1990s by ex-elite soldiers -- and their former bosses, the powerful Gulf cartel.

On Tuesday, the justice ministry said 22 suspected Zetas gang members were held in the latest arrests over the bodies unearthed in Tamaulipas.

The arrests brought the total to 55 detained, including 16 police officers and a suspected ringleader, for alleged involvement with the mass graves found in San Fernando.

Separately, officials in the state of Durango said 26 bodies had been found in mass graves there.

Durango is part of the so-called "golden triangle" of northern states -- along with Sinaloa and Chihuahua -- that has seen a vicious rise in unrest since authorities launched a crackdown on drug traffickers in December 2006.

Seven major drug cartels are embroiled in a violent drug war in Mexico that has left over 34,600 people dead during the past four years.