Prosecutor Rafael Curruchiche said that the complaint filed by an unidentified foreigner had raised serious concerns because it involved allegations of abuse of children.
Bernardo Arévalo was sworn in as Guatemala's president on Monday minutes after midnight despite months of efforts to derail his inauguration and rising tensions right up until the transfer of power.
In Guatemala, an anti-corruption candidate wins the runoff election by a landslide, in a vote that was a critical test of the Central American country's democratic credentials.
Guatemala's already troubled presidential election has been thrown into more chaos and confusion only weeks ahead of a contentious second round of voting.
Human rights groups have called the trial of journalist José Rubén Zamora a politically motivated sham after his newspaper uncovered corruption in the Central American country.