Mexican authorities began looking for bodies Monday at a new mass grave in the violent state of Veracruz, where hundreds of corpses have been found at similar sites in recent years.
The Solectio collective, a group of mothers searching for their missing children, said it learned about the site from an anonymous tip.
"The information we have is that there could be 400 to 500 bodies," said Rosalia Castro Toss, the group's spokeswoman.
"It was a death camp, or worse."
The site is located about five kilometers (three miles) from another mass grave, the Colinas de Santa Fe, where 296 bodies have been found so far.
Home to one of Mexico's largest ports, Veracruz is the scene of bloody turf wars between the rival drug cartels Jalisco New Generation and Los Zetas.
Corrupt officials are accused of colluding with the cartels during the administration of jailed ex-governor Javier Duarte.
A string of top security officials face charges of running police death squads that took out their enemies during Duarte's administration (2010-2016).
Mexico registered a record 28,711 murders last year, in violence driven mainly by its powerful drug cartels.
Since 2006, when the government deployed the army to fight drug trafficking, more than 200,000 people have been murdered. Another 30,000 are missing.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
Unidentified Gunmen Kill 13 At Mexican Party Mass Grave With Over 160 Skulls Could Be "Biggest In Mexico, Even World" In Mexico State Hit By Cartel Wars, Mass Grave With 166 Bodies Found Trainee IAS Officer Puja Khedkar Recalled To Academy, Training Put On Hold Under-Fire Trainee IAS Officer Accuses Pune Collector Of Harassment "No Defamatory Remarks Against Governor": High Court To Mamata Banerjee Study Abroad: Top 10 Affordable Universities In The UK Man Sets Mother On Fire Inside UP Police Station, Films Her Byju's Faces Insolvency Proceedings For Failure To Pay BCCI Rs 158.9 Crore Track Latest News Live on NDTV.com and get news updates from India and around the world.