MEXICO CITY – The Mexican government accused the Zetas drug gang on Tuesday of killing 116 people whose corpses have been found in a series of mass graves near the American border.

Police have detained 17 suspects and believe gunmen from the notoriously violent cartel dragged the victims off buses passing through the San Fernando area of northeastern Tamaulipas state.

"As of (Tuesday) we can confirm that a total of 116 people have been found dead as a result of criminal actions apparently caused by actions by the Zetas criminal group," Mexico's attorney general Marisela Morales told reporters.

Los Zetas, founded by deserters from the Mexican special forces and thought to have many corrupt former officials and ex-police on its payroll, is at the heart of the narcotics trade and organized crime in Mexico.

Engaged since February 2010 in a turf war for control of lucrative smuggling routes into the United States with the Gulf Cartel -- its former employers -- the cartel was blamed for the massacre of 72 migrants in August in Tamaulipas.

The largest concentration of graves ever found in Mexico was unearthed on Thursday in the San Fernando area, about 100 miles (160 kilometers) south of the Texan border, and the grisly toll has been rising steadily since.

Tamaulipas state officials say at least six buses have been attacked by gunmen this year and several passengers kidnapped. Residents tell local media the real toll is far higher.

Officials say two buses known to be missing were carrying mostly Mexicans, however Guatemala's foreign ministry said Tuesday that one of the bodies found in the graves was that of a 44-year-old Guatemalan man.

Separately, the US consulate in the Tamaulipas city of Matamoros said at least one American was kidnapped while traveling in one of the held-up buses.

Tamaulipas governor Egidio Torre Cantu met in Mexico City with Interior Minister Francis Blake on Tuesday to discuss the killings.

The Mexican military issued a statement on Sunday saying the graves had been discovered following information obtained from a suspect identified as Armando Morales Uscanga.

According to Morales, several of those killed were travelers aboard two long-distance passenger buses kidnapped between March 24 and March 29.

Morales acknowledged "his participation in the assassination and illegal burial of 43 bodies," the military statement said.

Los Zetas were also blamed back in August 2010, when officials in San Fernando found the remains of 72 people, mostly Central American migrants, who had been executed by criminals.

The motive suggested by the authorities was that the drug cartel was seeking to recruit young men into their gang and simply killed those who refused.

Some 35,000 people have been killed since 2006 when President Felipe Calderon launched a clampdown on the country's powerful gangs, involving tens of thousands of troops.