Mexico’s ultra-violent Zetas drug cartel has made connections and collaborated with U.S. gangs throughout the United States since at least 2010, a leaked, confidential FBI document revealed.

The FBI intelligence bulletin, published by the free information group Public Intelligence, showed that the Zetas have formed strong bonds with gangs of both Mexican and non-Mexican Americans to facilitate drug trafficking and enforcement on both sides of the border. The presence of Zetas-linked gangs is especially prominent along Texas’ southwest border and in Houston.

“The FBI judges with high confidence that Los Zetas will continue to increase its recruitment efforts and establish pacts with non-military trained, non-traditional associates to maintain their drug trafficking and support operations,” the report stated.

Experts argued that this move is a natural progression of the inroads Mexico’s cartels have made in the U.S. and other parts of the world. Associates of Mexico’s cartels already have a large presence in major U.S. drug trafficking hubs such as Chicago, Houston and Atlanta.

“They are trying to distance themselves from the middlemen,” said Adam Isacson, a senior associate from the Washington-based think tank the Washington Office on Latin America (WOLA). “We’ve seen this happening in the Andes and now it’s happening on our side of the border.”

The FBI bulletin revealed a 2010 Zetas deal with the Texas-based prison gang, the Mexican Mafia, to collect debts, carry out hits and traffic drugs in and through Laredo, Texas. The Zetas also bought AK-47 assault rifles from the Houston-based street gang Tango Blast and attempted to recruit a number of American citizens to join the cartel’s war against the Gulf Cartel.

This attempt to enlist American gang members into one of Mexico’s top drug cartels indicates that the Zetas have started to rely on non-traditional, non-military trained associates. Originally made up of former members of Mexico’s Special Forces, the Zetas are the former paramilitary-wing of the Gulf cartel and considered to be one of two dominant cartels in Mexico, along with Joaquín “El Chapo” Guzmán's Sinaloa cartel.

“It’s puzzling that they recruit non-trained people,” said Peter Hakim of the president emeritus of the Washington-based think tank, the Inter-American Dialogue. “They would want people who were well-trained and knew how law enforcement works. Maybe they are hiring people for jobs that do not require the skilled use of firearms or deadly tactics.”

There are also rumors that the Zetas have been weakened due to a split into two rival factions that are battling for control of the central states of Zacatecas and San Luis Potosi, as well as for parts of Yucatan peninsula. While authorities have not confirmed the split, local media and some experts claim that there is enough evidence of internal strife within the Zetas.

"If it is true, a split would likely hinder the ongoing attack on Sinaloa groups and strongholds, as Zeta groups turned on each other," Shannon O'Neil, a Douglas Dillon Fellow for Latin America Studies at the Council of Foreign Relations, told Fox News Latino. "With this different dynamic, it is unclear that the levels of violence would change – killings would continue, the 'teams' and actors may have shifted."

While the Colombian drug cartels of the 1980s and 1990s made wide connections throughout the U.S., these reports indicate that Mexican cartels have stepped up their efforts to take a more central role in the trafficking of their products north of the border.

A wide-ranging Associated Press review, released earlier this month, of federal court cases and government drug-enforcement data, plus interviews with many top law enforcement officials, indicate the groups have begun deploying agents from their inner circles to the U.S. Cartel operatives. They are also suspected of running drug-distribution networks in at least nine non-border states, often in middle-class suburbs in the Midwest, South and Northeast.

"It's probably the most serious threat the United States has faced from organized crime," said Jack Riley, head of the Drug Enforcement Administration's Chicago office.

Besides the U.S., Mexican cartels – particularly the Sinaloa group – have expanded their operations across the globe.

The U.S. Drug Enforcement Agency (DEA) recently announced documented links between Mexican cartels and criminal groups in Mozambique, the Democratic Republic of the Congo, Ghana, and Nigeria. The Sinaloa Cartel is also known to have ties not only in Europe but throughout Latin America, Africa, Asia and Australia, where a booming trade has developed in the country’s cities.

“It’s not surprising,” Isacson said of the cartel expansion around the globe. “The power of the Mexican cartels keeps growing both upstream and downstream.”

The Associated Press contributed to this report.

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