Mexico's domestic intelligence agency was once so paranoid it even spied on members of the former ruling party.

One such member was current President Andres Manuel López Obrador, who previously belonged to the Institutional Revolutionary Party.

The government released Tuesday a trove of old intelligence documents drawn up by spies in 1979 and 1980 from the now-extinct Federal Security Department. A few claimed López Obrador was a local leader of the Mexican Communist Party.

López Obrador left the PRI party in 1988 and won the presidency last year.

Upon taking office, he opened up old intelligence archives from the dissolved agency.

The president has said: "I was not a member of the Communist Party, but I did support social activists."