Mexican authorities have uncovered another mass grave, this time in northern Mexico. They pulled 37 decomposed bodies from the site in Durango yesterday and Wednesday, reports Reuters. Two rival drug camps, the Zetas and Sinaloa cartels, have been battling for control of the region, notes AP. The development comes after the discovery of an even bigger mass grave in the border state of Tamaulipas last month. The total there is now 177. An estimated 37,000 people have been killed in the nation's drug war over the past four years. (More Mexico stories.)