Mass grave Mexico
View of one of the graves in Veracruz state, Mexico on June 18, 2014, where the bodies of at least 28 people have been exhumed. STR/AFP/Getty Images

A mass grave containing at least 28 bodies has been found by authorities near a ranch in the town of Tres Valles in Veracruz, east Mexico.

After the discovery, federal and state police forces guarded the area, while people with missing relatives or friends went to the police offices to check the identity of the victims. The authorities said the numbers of corpses could increase.

The motive behind the mass killing is still unknown, but it is suspected that drug cartels in the area may be behind it.

Drug cartels in Mexico operate with a degree of impunity and systematically kidnap, torture and execute people in the struggle for control of drug trafficking across Mexican territories.

Some of the deadliest clans include Los Zetas, which controls the most territory in Mexio and which often posts videos online showing the killing of people. The Knights Templar, the Gulf Cartel and the Jalisco New Generation Cartel (JNGC) are also well known for their brutality.

Los Zetas, the Gulf Cartel and JNGC operate in Veracruz. Executions are often carried out to intimidate members of competing clans.

Officials have discovered several mass graves around Mexico in recent years, some of which containing the bodies of migrants.

Hundreds of Central America migrants travel to Mexico each year and they are often killed by drug cartels which control the migrant-smuggling routes.