McQuay, 44, who claimed to have molested hundreds of children, could be held in prison until 2016, the end of his original 20-year sentence on three counts of indecency with a child.
His request to be castrated led the Texas Legislature to make it available in 1997. At least three Texas inmates have undergone the surgery with hopes of curbing sexual desire, though medical professionals are unsure of its effectiveness.
McQuay was released from prison in 2005 and was living at a Bexar County work-release facility under heavy supervision, including an ankle monitor, until authorities say they found the sexually explicit materials last month.
Possessing the material would be a violation of McQuay's release terms. Lyons did not say whether the material was child pornography, or how McQuay is alleged to have acquired the material.
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