
Raúl Sánchez said he had asked for information about the missing Italians from Italian police
But their relatives in their hometown of Naples denied that the three were doing anything illegal in Mexico.
The relatives were the first to alert the authorities that the men were missing, saying that they had received a phone call from one of them in which they mentioned being stopped by a police patrol.
Following their disappearance, the town's entire police force was sent for retraining, although some local media speculated that they were sent away so that they could not be intimidated by local cartel members into changing their story.
The four officers who have been detained, three men and a woman, have been charged with forced disappearance.
Mexican media have drawn parallels between this case and that of 43 Mexican students who disappeared from the town of Iguala in 2014.
The state prosecutor in that case said that the students were handed by corrupt local police to a criminal gang, who killed them and burned their bodies.
Local police, who are poorly trained and poorly paid, are often threatened or bribed by criminal gangs to turn a blind eye or even do their bidding.
For that reason, federal authorities often send federal police forces and even soldiers to the most violent areas.