Two serving and one former mayor in the western Mexican state of Michoacan are being held over allegations they have links to a notorious drugs cartel.
A federal judge has ordered they be charged with organised crime.
The move follows the publication on social media of videos showing them apparently meeting the leader of the Knights Templar cartel.
The Knights Templar control much of the methamphetamine and marijuana trade in western Mexico.
The federal chief of criminal investigations, Tomas Zeron, said the mayors of the towns of Huetamo and Patzcuaro, Dalia Santana and Salma Karrum, as well as the former mayor of Lazaro Cardenas, Arquimides Oseguera, would be charged.
Mr Oseguera was arrested back in April when he was still mayor of the port of Lazaro Cardenas, a stronghold of the Knights Templar.
Ms Santana and Ms Karrum are under arrest in Michoacan and Mexico City respectively.
Knights Templar Cartel
- First emerged in 2011 as an offshoot of La Familia Michoacana drug cartel
- Takes its name from a Christian military order from the Middle Ages
- Claims to protect Michoacan residents from kidnappings, extortion and robberies committed by rival gangs
- Controls much of the methamphetamine and marijuana trade in western Mexico
Mr Zeron said his office had obtained videos showing the three had had “at least two meetings” with Servando Gomez, the leader of the Knights Templar, also known as La Tuta.
The police have arrested or killed three out of the four main leaders of the Knights Templar over the past year but La Tuta remains at large.
Michoacan residents have long complained about alleged collusion between local government and the Knights Templar.
They say cartel members extort them and engage in kidnapping and intimidation.
In January, vigilante groups formed by disgruntled residents tried to expel the group from the region.
The vigilantes took control of several towns before federal forces were deployed to the area.
The Mexican government invited the vigilantes to join the official security forces and carry on the fight against the cartel.