MEXICO CITY (Reuters) - Mexican authorities said on Tuesday they had asked Rome for a criminal background check on six Italian citizens, after three of them went missing in the western Mexican state of Jalisco at the end of January, allegedly at the hands of local police.

The attorney general’s office in Jalisco said at least one of the Italians was arrested three years ago in the tourist beach resort of Cancun, but gave no details.

“We are asking Italy for records for all of them, not just the three that went missing,” Jalisco attorney general Raul Sanchez told reporters. “But also for the three people that were with them, because we know that it was six of them.”

On Monday, authorities said they were investigating whether police in Jalisco participated in the reported Jan. 31 disappearance of the three Naples natives, who had been detained at a gasoline station in the state’s southern municipality of Tecalitlan.

Sanchez said the Italians were not in Mexico as tourists, but instead selling fake-brand power generators and other tools, passing them off as name brands.

Another Italian was arrested on Tuesday in neighboring Guanajuato state for selling the same type of products, Sanchez added.

Mexico is grappling with its worst-ever surge in violent crime, with more than 25,000 killings in 2017, as rival drug gangs splinter into smaller groups and dispute territory.

In Mexico’s most violent states, corrupt policemen often collude with criminal gangs.

The Jalisco New Generation Cartel, regarded by the United States as one of Mexico’s most powerful drug gangs, operates in Jalisco.