A mass grave of 31 bodies has been discovered in the eastern state of Veracruz, Mexico.

The location of the grave at a farm near the border with the state of Oxaca was discovered after an anonymous tip-off to police.

Forensic experts are examining the grave in an effort to find out clues as to how and why the people were killed and buried there, but it is likely that the deaths are a result of the violent clashes between rival drug gangs in the region, such as the Zetas and the Gulf Cartel.

Mexican authorities have unearthed a number of mass graves in recent years as the bodies have mounted in the fierce fighting between rival gangs over territory and control of the illegal trade.

The Trans-Border Institute estimate that more than 120,000 deaths can be attributed to drug-related violence since 2006.