NEW YORK -- Newly unsealed documents about notorious Mexican drug lord Joaquin "El Chapo" Guzman contains claims by witnesses that he had sex with minors he called "vitamins," a disturbing allegation coming just as a jury is about to start deliberating in his U.S. drug-trafficking case.

According to papers made public late Friday, a key government co-operator told authorities Guzman had him drug girls as young as 13 before Guzman had sex with them at one of his Mexican hideouts in the late 2000s.

One of Guzman's lawyers called the accusations "extremely salacious" Saturday, and questioned the timing the government filing.

Guzman "denies the allegations, which lack any corroboration and were deemed too prejudicial and unreliable to be admitted at trial," attorney Eduardo Balarezo said in a statement. "It is unfortunate that the material was publicly released just prior to the jury beginning deliberations."

The jury is to set to begin deliberations Monday after a nearly three-month trial on charges that as the head of the Sinaloa cartel, Guzman oversaw a drug-smuggling empire that flooded the U.S. market with at least 200 tons of cocaine and made $14 billion off of it. The defence has said co-operating witnesses have made Guzman a scapegoat for their own crimes.

The unsealing of the documents came at the request of The New York Times and Vice News. U.S. District Judge Brian Cogan had ordered prosecutors to review the material -- sealed because it was deemed unrelated to the drug charges -- and make portions of it public within four days after they rested their trial case against Guzman.

One document says Colombian drug trafficker Alex Cifuentes, while living with Guzman around 2007, told investigators someone known as Comadre Maria would offer photos of young girls to Guzman. For $5,000, the one of Guzman's choice would be sent to one his secluded Sinaloa ranches, Cifuentes said, according to the papers.

Guzman directed Cifuentes to put a "powdery substance" into the girls' drinks before sex, said Cifuentes. Guzman "called the youngest of the girls his 'vitamins' because he believed that sexual activity with young girls gave him 'life,"' he added.

Cifuentes also admitted having sex with minors but without drugging them.

The document says other co-operating witnesses have backed up Cifuentes' allegation.