The bodies of 14 people have been discovered in the northwestern Mexican state of Zacatecas.
They were buried in a grave in a mountainous area of Valparaiso.
Federal and state forces have been carrying out raids in recent days to find a criminal gang thought to be operating in the area.
Authorities believe the grave could be linked to the group which has carrried out robberies, kidnappings and extortion.
"We have found 14 bodies that correspond to eleven men and three women. In some cases the bodies are dismembered, some are handcuffed and others are recent bodies," Zacatecas prosecutor Francisco Murillo told a news conference.
Three suspects have been detained. They are said to have been working for gang run by a criminal leader called Bernardino, aka Commandant Gabacho.
The three detainees were captured on 1 August in Valparaiso and transferred to the Federal Public Prosecutor's Office in Fresnillo.
After the arrests, armed individuals attacked the facilities of the federal complex and the House of Justice in Valparaíso.
Two Mexican army soldiers were injured in the incident, one of them died later.
Mass graves, some containging hundreds of bodies, have been discovered in Mexico in the states hardest hit by drug violence, such as Tamaulipas, Veracruz, Morelos and Guerrero.
Between January and May of 2017, 12,238 homicides were recorded across the country, according to numbers provided by the Attorney General's Office.
However, during this period, the Attorney General's Office has undertaken to investigate only 415 of these cases.
According to the annual Armed Conflict Survey by the International Institute for Strategic Studies, IISS, the number killed in 2016 due to the expanding drug war in Mexico makes the country among the most dangerous in the world.