One of the hitmen that the infamous Joaquin “El Chapo” Guzman trusted to do his dirty worth kept a soundproof room complete with a drain in the floor to make cleaning up mess killings easier, a witness has told court.

“He took me once to a house, where the floor was just white, tiled,” Edgar Galvan, a government witness in the case against Mr Guzman, said of alleged hitman Antonio “Jaguar” Marrufo.

“That’s where he killed people,” he testified on Monday in a New York City federal courtroom.

Testimony indicated the room was somewhere in Mexico’s Ciudad Juarez.

Mr Galvan told prosecutors that he was informed that the room was sound proofed “so no noise comes out”, and that nobody leaves the house once they enter.

The witness said that he had accidentally come upon the world of drug trafficking in 2007, after he divorced from his wife and started going to clubs.

He testified that he had not met Mr Guzman before his testimony on Monday, and that Mr Guzman's general position in the cartel was to help run guns over the border to help kill off rival cartels.

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Once the “cleaning” of Juarez had taken place, he said, Mr Guzman could then control the areas, Mr Galvan told the court.

Mr Galvan was arrested in 2011 and pleaded guilty to possessing narcotics and firearms. He is currently a third of the way through a 24-year sentence.

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Mr Guzman has pleaded not guilty to the 17-count indictment he faces. Those charges include murder conspiracy, the distribution of cocaine, and firearms possession.