Story highlights The use of human fetal tissue has been a political flashpoint since the 1990s

Grassley's 2016 report claimed US agencies had failed to monitor the industry

(CNN) The Justice Department is looking into Planned Parenthood's practices related to human fetal tissue, according to a letter obtained by CNN on Thursday.

The letter -- from the Justice Department's head of its Office of Legislative Affairs -- does not mention Planned Parenthood by name but asks the Senate Judiciary Committee to turn over unredacted documentation supporting a December 2016 report titled "Human Fetal Tissue Research," which purports to describe the organization's practices.

"At this point, the records are intended for investigative use only," Assistant Attorney General Stephen Boyd wrote. "We understand that a resolution from the Senate may be required if the Department were to use any of the unredacted materials in a formal legal proceeding, such as a grand jury."

"Yesterday evening the committee received the Justice Department's request and we're going to work to comply with that request," Taylor Foy, a spokesman for Senate Judiciary Chairman Chuck Grassley, confirmed to CNN on Friday.

The use of human fetal tissue -- which is used to study a number of diseases -- has proved to be a political flashpoint for decades.

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