The Organization of American States released its final report Wednesday into the October election in Bolivia, concluding that "malicious manipulation" had affected the vote, which has tipped the country into turmoil.
Incumbent president Evo Morales, who had been seeking a fourth term after ruling for nearly 14 years, claimed a narrow victory, but opposition groups accused him of rigging the results.
Isolated and abandoned by the police and military, Morales resigned on November 10 and fled to Mexico, where he was granted political asylum.
"The audit team detected malicious manipulation of the elections," the OAS said in its report.
"Based on the overwhelming evidence, what is possible to say is that there was a series of malicious operations aimed at altering the will expressed at the polls."
After Morales fled, right-wing senator Jeanine Anez declared herself interim leader and has since authorized a new ballot that excludes Morales, though no date for the vote has been set.
Anez's government has blamed foreigners for provoking violent clashes during more than a month of post-election violence in Bolivia that has left dozens of people dead.