CHICAGO (CBS) — A top lieutenant of the drug kingpin ‘El Chapo’ is being held in Chicago where he faces federal drug charges.

CBS 2’s Derrick Blakley reports the feds have had Edgar Manuel Valencia, also known as the “Fox,” in custody since January. His arrest was a secret until Wednesday when federal court documents were unsealed.

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Joaquin “El Chapo” Guzman, kingpin of the notorious Sinaloa drug cartel, was arrested in February in Mexico, but capturing the biggest fish was just start of federal efforts to dismantle his criminal empire.

According to former FBI agent Ross Rice, Chicago figures prominently in the Sinaloa cartel’s operations.

“The are responsible for the vast majority of illegal of the drugs brought into this country, brought primarily through Chicago,” said Rice.

Valencia Ortega was arrested in at the Las Vegas airport January 26 after arriving from Mexico. Two days later, he was flown to Chicago, but detained in the Oak Park police station.

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According to court documents, “…this was done to preserve the possibility that he might agree to cooperate with the government without this becoming known to others.”

In other words, the feds tried to squeeze Valencia by threatening to add him to the El Chapo conspiracy case and on February 27, they did just that.

Prosecutors say they’re looking to seize cash and property derived from El Chapo’s drug operations that’s worth an estimated $1.4 billion and perhaps even more.

Although Joaquin “El Chapo” Guzman was arrested in February, he still hasn’t been extradited to Chicago. If he is, he could be tried alongside Valencia in federal court.

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Another alleged Sinaloa member, Alfredo Vasquez-Hernandez, is due to stand trial in May.