Mexico's drug corruption scandals reached into the presidential guard as authorities identified an officer who served in the unit as a possible spy for the country's violent drug cartels.

An official of the federal prosecutor's office who was not authorized to be quoted by name identified Arturo Gonzalez Rodriguez on Saturday as an army major who was assigned to a unit of the presidential guard.

Prosecutors announced on Friday that Gonzalez Rodriguez had been placed under house arrest for 40 days while he is investigated.

The prosecution official said there are allegations that the officer passed information to the Beltran Leyva drug cartel in exchange for payments of as much as $100,000.

The prosecutor's office could not confirm what type of information the major purportedly passed to drug traffickers.

But an official of President Felipe Calderon's office said that Gonzalez Rodriguez wasn't part of the elite section of the guard that takes care of Calderon's personal security or logistics.

The official, who was not authorized to be quoted by name, stressed that Gonzalez Rodriguez never had access to any information about Calderon's activities.

In a 2007 interview with The Associated Press, Calderon said members of the federal government have received threats from traffickers.

"There have been a lot of threats _ whether they have been false or real _ but they won't stop us from taking action," Calderon said.

More than a dozen high-ranking police and prosecution officials have been detained on similar allegations of spying for cartels in recent months, but none has been linked so closely to the president's office.

Soon after Calderon took office two years ago, he launched a nationwide offensive to take back territory controlled by drug gangs, deploying more than 20,000 soldiers.

In recent months, his administration also launched Operation Clean House, to combat corruption in the nation's law enforcement agencies.