Thirteen of 18 people arrested in an operation targeting a criminal gang in the Mexican resort city of Acapulco are active-duty federal police, government security spokesman Eduardo Sanchez said Tuesday.

The 18 suspects, thought to be involved in seven homicides and four kidnappings, were arrested during the period Oct. 2-4 thanks to a tip from the public, the spokesman told a press conference in Mexico City.

Sanchez said that the band, apparently headed by Luis Miguel Gonzalez, "operated exclusively in Acapulco," but he refused to give additional details so as not to compromise the ongoing investigation.

He emphasized that currently an "exhaustive investigation" is under way on all the members of the band to determine if more people are involved, and he urged the public to continue reporting the whereabouts of any alleged criminals.

"Under no circumstances are we going to tolerate impunity" or acts of corruption "on the part of any public servant," Sanchez said.

He added that so far during the administration of Enrique Peña Nieto, who took office on Dec. 1, 2012, "81 federal police who were surprised committing some illicit act" have been arrested.

The National Statistics and Geography Institute calculates, on the basis of a public survey, that in 2012 there were 105,682 kidnappings in Mexico.

When asked about that figure, Sanchez admitted that with crimes like kidnapping and extortion there is an "enormous dark number" because citizens who are subjected to them frequently do not report them to the authorities out of fear of reprisals. EFE