El Chapo Sean Penn Under Investigation

1/10/2016 6:39 AM PST BY TMZ STAFF

0110-sean-penn-kate-el-chapo-01The Mexican government is conducting an investigation targeting Sean Penn and a Mexican actress for secretly meeting with and interviewing drug lord El Chapo ... according to ABC news.

The basis of the investigation is unclear -- the interview was conducted in October in Mexico, when Chapo was still on the run.

It appears authorities knew Penn and actress Kate del Castillo -- who facilitated the meeting and had gained Chapo's trust -- had hatched a plan to do a sit-down with Chapo.  

Penn wrote in Rolling Stone he believed the DEA became aware he was going to travel to Mexico for the interview, adding, "Booking any flight to Mexico now would surely raise red flags ... I made a plan to hide myself in the trunk of a friend's car and he drove me to a waiting rental vehicle."

It's unclear if the U.S. government knew of Penn's plan or if they're currently investigating.