According to the official report published by the Mexican Navy, citizens reported "armed people" in a house at the coastal city of Los Mochis in northern Sinaloa, which was then placed under surveillance for one month. Monitored communications indicated the home was being prepared for the arrival of "Grandma" or "Aunt", which authorities suspected was code for a high-priority potential target. After the gunmen returned to the house, placing a large order for tacos at a nearby restaurant and picking up the order in a white van after midnight, the residence was raided in the early hours of 8 January 2016, in Operation Black Swan, by 17 marines from the Mexican Navy's Special Forces with support from the Mexican Army and the Federal Police – but Guzmán and a lieutenant escaped through a secret tunnel, emerging 1.5 km away and stealing a vehicle at gunpoint.