Mexico City (CNN) -- At least 21 federal prosecutors in Mexico have resigned in the past four days, an announcement that comes on the heels of a purge of agents and investigators in the attorney general's office.
Mexico's federal attorney general's office, known by its Spanish initials PGR, said that the prosecutors stepped down by their own will, though it remained unclear why it happened en masse.
The prosecutors who resigned were the federal delegates of the attorney general's office in the different states, a position similar to that of a U.S. attorney in the United States.
As of Tuesday, 65% of Mexican states and the federal district were without a top prosecutor.
Last month, Attorney General Marisela Morales said that she was overseeing the dismissal of the 140 police officers and investigators and has more than 280 others under investigation.
The shake-up at the agency, which plays a pivotal role in the country's fight against the drug cartels, is the most public show of transparency in recent history.
None of the federal prosecutors who resigned are under investigation, the PGR said.