The United States government has been aware for so long about "Arab extremists" entering the country and using Mexico as their channel, state department documents revealed.

In a Judicial Watch exclusive, it was indicated that US had knowledge of these individuals coming into the country with the aid of smuggling network cells in Mexico.

The documents disclosed that among those who penetrated the country using these "cells" was Al Qaeda leader Adnan G. El Shurkrjumah, who was under the Federal Bureau of Investigation's (FBI) watch list.

According to CNN, Shukrijumah, who was wanted for his connection to the terror attack plans in Pakistan and the United Kingdom, was killed last December 2014 by the army in Pakistan.

He was also believed to be involved in the 2010 plan to have two suicide bombers kill themselves in the New York City subway.

Judicial Watch added that Shukrijumah also had a hand in the plan to bomb Oprah Winfrey's Harpo Studios and the Sears Tower, both in Chicago.

An InfoWars report added that that the most wanted terrorist was able to cross back and forth into the US and schooled meetings with other militant Islamists in Texas.

He even reportedly flew an aircraft going to Cielo Dorado, Anthony in New Mexico.

But CNN highlighted that although Shukrijumah was born in Saudi Arabia, he moved to the US when he was young.

His family established residence in Brooklyn, New York, where his father worked as a preacher at a mosque.

While he was in the US, the terrorist was believed to have odd jobs like selling second-hand cars. He also reportedly studied in South Florida, where he took up a course in chemistry and information technology. Shukrijumah exerted effort to learn the English language by enrolling himself in classes that helped him adopt to his new hometown.

His co-conspirators in his terrorism plans -- Emad Karakrah and Hector Pedroza Huerta -- have already been arrested in 2014 in the United States.

Aside from this information, the state documents also detailed that smuggling networks in Mexico provide logistical help to Arabs who want to get onto US soil.

PJ Media noted that the revelation of these documents was not really surprising since "the ranks of 'immigrants' from Latin America have suddenly swelled as the legion of 'migrants' from the Islamic region."

It explained that this has since caused the thriving of drug cartels in the United States because of the illegal crossing of borders. The same report blamed the past and present administration for being lenient in terms of border security.