A senior member of Mexican President Vicente Fox's staff has been arrested over possible links with a drugs gang.
Mr Nahum Acosta, a senior member of Fox's secretary's office, was arrested on Thursday on suspicion of leaking information about the president's activities to a criminal gang linked to drug smuggling.
The country's attorney general Mr Rafael Macedo said. "At this time, I can refer to a criminal organization, in which we are sure who his link was. It's an organization linked to drug trafficking."
Mr Acosta had been working since 2001 as a senior member of the team that organizes Mr Fox's official trips.
While there was no security risk to Mr Fox, it was worrying that a crime gang could have infiltrated a presidential institution, Mr Macedo said.
Prosecutors are pursuing their investigation in various parts of Mexico but mainly the central state of Mexico, home to a number of prisons, including the maximum-security La Palma jail, that hold drug barons.
"This is one more illustration that this is working and that we are going to go as far as we have to go. We are not going to give these criminals any space," Mr Macedo added, referring to Mexico's war on drug smuggling.
In recent weeks and months Mexico has stepped up its fight against drug gangs, launching what Mr Fox has called "the mother of all battles" against the cartels that terrorize parts of northern Mexico.
Amid a crackdown on prisons, hundreds of army troops have occupied La Palma, where imprisoned mobsters have taken advantage of lax regulations to order killings and organize narcotics trafficking from their cells.
Mr Fox, angered by charges from the US ambassador last month that the Mexican police were losing the battle against crime on the US-Mexican border, called for the United States to work with Mexico against narcotics trafficking.