At least 51 bodies have been discovered in nine unmarked graves in northern Mexico, officials say, in one of the more grisly recent turns in the country's rampaging violence linked to drug gangs.
Many of the victims, found earlier in the week in a series of graves located in a suburb of Monterrey, the capital of Nuevo Leon state, had their hands bound and showed signs of torture, investigators said.
"There are 51 bodies that have been discovered so far," all but two of them male, state prosecutor Adrian de la Garza told a local television station. Officials said the victims had likely been dead for about 15 days.
The bodies, several of them bearing tattoos which investigators were studying, were exhumed beginning on Friday, when authorities said the remains of 38 people had been found. But on Saturday they announced the figure had risen by 13.
Authorities brought freezer trucks to the site to preserve the corpses, so that residents in and around Monterrey who were missing relatives could come to try to identify the remains.
The bodies were in an area spanning 3 hectares (about 7 acres) in the municipality of Juarez outside the state capital of Monterrey. Investigators were still searching for additional graves Friday, he said, according to Notimex.
The bodies were mostly males between ages 20 and 50, Notimex said, and many of them had tattoos.
Forensic investigators are performing DNA tests to identify the victims, Notimex reported.
Similar mass graves have been discovered in the Mexican states of Tamaulipas, Guerrero and Quintana Roo since late May. Authorities have linked them to Mexico's ongoing drug war.
Nuevo Leon, which borders Texas, has seen a spike in drug violence this year due to an intensifying rivalry between former partners: the Gulf cartel and a group know as the Zetas.
It is the second major finding this year of bodies deposited in mass graves, allegedly by members of Mexico's warring drug cartels, after the remains of 55 people were exhumed in June in the southern state of Guerrero.
Metropolitan Monterrey is the nation's industrial centre, and over the last several months it has become a drug war battleground, pitting the Gulf cartel against its former allies the Zetas, a gang of hitmen formed by ex-soldiers.
Around 25,000 people have died in rising drug violence across Mexico since President Felipe Calderon launched a military crackdown on organised crime three and a half years ago.