Video shows National Guard officers enter home minutes before 4 women and 2 children were killed in Mexico

Mexico's President Andrés Manuel López Obrador said Tuesday that investigators are looking into the killings of four women and two children in central Mexico, where security video shows National Guard officers were present.

The murders occurred Sunday in León, an industrial city in the state of Guanajuato where drug cartels have been fighting bloody turf battles for years.

The quasi-military National Guard has been López Obrador's main force for battling organized crime, though the military has been implicated in a series of human rights abuses that are tainting the Guard.