(CNN) The body of a missing Mexican butterfly conservationist and activist has been found, authorities confirmed.

Homero Gomez Gonzalez, 55, had been missing since January 13, police told CNN Espanol. He was found in Ocampo, Michoacán state, Mexico President Andres Manuel Lopez Obrador said at a Thursday press conference.

Homero Gomez

Lopez Obrador called Gomez's death "lamentable and painful" and vowed to continue to fight criminal groups believed to be behind his disappearance and death.

According to the Michoacan prosecutor's office, Gomez's body was found with a head injury and he died of drowning. His body was found in a retention pond. An earlier report indicated it was in a well.

An official autopsy will be released at a later date.

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