Mexican authorities initially said there was no evidence the kidnapping had taken place.

Alejandro Solalinde, a Roman Catholic priest and migrant rights activist who first reported the abductions, said witnesses told him the kidnappers have ties to the Zetas drug gang.

The Attorney General's Office didn't say who the suspects were working for.

In a separate case, a man and a woman were arrested in the Dec. 22 kidnapping of nine migrants also in Oaxaca, the office said.

Five of those migrants escaped and reported the kidnapping. Another was killed as he tried to flee and the other three remain missing.

The office said the couple forced the group to walk through the mountains and demanded phone numbers for their relatives. The kidnappers demanded $500 for the release of each migrant, it said.

Prosecutors said a third case involved the arrest of a woman they allege guarded 13 kidnapped migrants in neighboring Veracruz state.

Mexico is the transit route for thousands of illegal migrants seeking to reach the United States, with many falling victim to gangs and organized crime.

In the most horrifying case to date, 72 migrants were found shot to death in the northeastern state of Tamaulipas in August. The massacre was blamed on members of the Zetas drug gang.