(CNN)The New York attorney general's office has subpoenaed two of former President Donald Trump's children for testimony as part of its civil investigation into whether the Trump Organization manipulated the values of its properties.

       The disclosure was made public Monday in a court filing where the judge set a briefing schedule to handle a dispute that has arisen over the subpoenas for Trump's testimony as well as Ivanka Trump and Donald Trump Jr.

       The attorney general's office previously subpoenaed Trump for testimony and set a deadline of January 7. Trump's lawyers have said they would move to quash the subpoena.

       A lawyer for Ivanka Trump and Trump Jr. did not respond to a request for comment.

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       Eric Trump, an executive vice president at the company, was previously subpoenaed and provided his testimony in late 2020.

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       The subpoenas for the testimony of Trump's children comes amid an ongoing criminal investigation into the Trump Organization and its executives and whether they inflated the value of some of its assets. Prosecutors with the Manhattan district attorney's office have interviewed additional witnesses in that case in recent weeks. The New York attorney general's office joined with the district attorney as part of the criminal investigation earlier this year.

       The Trump Organization said state Attorney General Letitia James' investigation is politically motivated.

       "Letitia James is the single most unethical Attorney General this country has ever seen," said Alina Habba, an attorney representing the Trump Organization. "The way she has weaponized her office through this political witch hunt exceeds all bounds of prosecutorial standards and violates basic constitutional rights. Her actions are a threat to our democracy and I plan to hold her accountable to the fullest extent."

       Trump sues NY attorney general, seeking to stop investigation into his company

       The Trump Organization sued James' office last month alleging she is biased and her investigation into the former President and his company is unconstitutional. It has asked a judge to block the civil investigation.

       James' office said in a statement that the Trump Organization has repeatedly attempted to delay her office's investigation into its business dealings, adding, "Our investigation will continue undeterred because no one is above the law, not even someone with the name Trump."

       This story has been updated with comment from the Trump Organization .