The newspaper Excelsior has reported that the Mexican government of then-president Felipe Calderon struck a deal with the US State Department in 2007, allowing the installation of a system to intercept, process, analyse, and store phone calls as well as emails and web chats.
The federal attorney general's office "is reviewing the documents and an investigation is underway" to determine whether a crime was committed, interior ministry spokesman Eduardo Sanchez told a news conference.
The system made its way to Mexico under the now-defunct Federal Investigations Agency (AFI) and the federal attorney general's office, in the name of combating drug trafficking and terrorism, the report said.
The equipment was sold by Verint Systems under a $3 million contract, the report said.
Sanchez said investigators are verifying whether the contract exists, and what its status is.
Calderon's 2006-12 administration cooperated deeply with the United States in the fight against drug cartels, with Washington earmarking $1.9 billion in aid that included law enforcement training and equipment.
President Enrique Pena Nieto, who took office in December, vowed to continue the security cooperation, but with one major change: He now requires US law enforcement agencies to filter all security matters through the powerful interior ministry instead of a previous arrangement that allowed them to deal directly with individual counterparts.