Two dogs named Baguira and Chihuahuitas were fundamental to guarantee the safety of Joaquin 'El Chapo' Guzman during his stay at a Juarez prison, according to the Mexican television network Televisa.
It reports that in the last two months of his stay, the two dogs would try the food that was served to the drug lord before it was given to him.
If Baguira and Chihuahuitas did not show any strange symptoms or discomfort, then the guards gave the food to Guzman.
Guzman was handed over to U.S. authorities for transportation to the U.S. on January 19, the last full day of former President Barack Obama's administration and a day before President Donald Trump was to be inaugurated.
The convicted Sinaloa cartel boss was recaptured in 2016 after escaping from a second maximum-security prison through a tunnel dug to his cell.
The 2015 escape was highly embarrassing for the government of President Enrique Pena Nieto, and Mexican officials were seen as eager to hand the headache off to the United States afterward. Guzman's lawyers have fought extradition since his recapture.
Guzman, who is in his late 50s, faces the possibility of life in a U.S. prison under multiple indictments in six jurisdictions around the United States, including New York, San Diego, Chicago and Miami.