Drones are a controversial subject in the United States, and the topic might carry across the country's southern border soon.

According to a report from Stars and Stripes on Monday, drones in Texas have been used to keep an eye on Mexico, in particular the drug cartel. The newspaper received paperwork that states the U.S. was using the air crafts across borders for security reasons.

"Need to be careful here as we are admitting to spying on Mexico," the internal document, which was written by a Virginia-based contractor in 2010, stated.

State officials are denying the report.

"This document was developed by an outside vendor, and it is imperative to make clear that the department unequivocally rejects the reference to 'spying,''' spokesman Tom Vinger said in an email. "This characterization does not reflect the department's position nor was this ever used as a talking point."

According to the document, the drones were keeping tabs on the movements of the Los Zetas drug cartel. A direct portion of the document explains what a particular drone's job was:

"...monitor suspected Zeta points of interest and pass this information on to Immigration and Customs Enforcement (ICE)... Using this information, ICE can work in conjunction with Mexican Military forces to target los Zetas both north and south of the border to disrupt cartel trafficking operations."

Phil Jordan, former director of the Drug Enforcement Administration's El Paso Intelligence Center, told Stars and Stripes that border patrol's job does not ential what the internal document alleges.

"It sounds like they were trying to do work that is a responsibility of the U.S. federal government," he said.