(CNN) -- A man who admitted a plot to blow up New York City subway stations with bombs planted in backpacks told his uncle that chemicals and other apparent bomb-making elements were "to manufacture a fertility medicine," according to court papers.
The uncle, Naqib Jaji, has pleaded guilty to his role in conspiring to destroy evidence in the case against his nephew, Najibullah Zazi. Zazi, who pleaded guilty last year to a plot to detonate explosives in subway stations in September 2009, is awaiting sentencing.
The uncle, Jaji, agreed to cooperate with the government as part of his guilty plea, according to federal court papers.
Jaji pleaded guilty in January, 2010, but the plea was kept under seal because prosecutors said they were worried about Jaji's safety. Prosecutors moved to unseal the plea this week.
Government documents quote Jaji as saying he allowed his nephew to live with him in Denver after his nephew returned from Pakistan with two other friends in 2008.
Around July 2009, "Jaji discovered gallon-sized bottles of toilet bowl cleaner in his garage, as well as an electronic scale, a protective mask, goggles, bottles of nail polish, and other bottles of a liquid substance in a cooler, " court papers state.
When Jaji challenged Zazi about the materials, he got an incredible explanation.
Zazi told his uncle "that he was using the chemicals to manufacture a fertility medicine," according to the government documents.
"The next morning, Jaji discovered that most of the items were gone."
The following month, Zazi moved out of his uncle's home. Prosecutors say Jaji later was told to get rid of any chemicals left behind in his home.
Court papers state several bottles of liquids were poured down a bathroom drain, and items including a protective mask and goggles were cut up and put in a dumpster.
Jaji is currently working as a taxi driver. The government, in a letter to the court, said he does not pose a risk and is subject to electronic monitoring.
Zazi's father, Mohammed Walid Zazi, is scheduled to go to trial in July in Brooklyn, New York.
Zazi co-defendant Zarein Ahmedzay also has pleaded guilty to his role in the plot. A third alleged plotter Adis Medunjanin has pleaded not guilty and is scheduled to go to trial next January.