The Democrat-led House is reportedly investigating whether President Donald Trump lied in his written statements to former special counsel Robert Mueller as part of his Russia probe, multiple outlets reported Monday.

CNN first reported that House general counsel Douglas Letter told a federal appeals court in Washington that Trump "might have provided untruthful answers" as part of the now-completed Russia probe and that the matter is "a key part of the impeachment inquiry" being conducted in the House.

Letter's arguments came as part of the House's bid to access the grand jury materials Mueller collected over the course of his investigation. Some of the grand jury details in the 448-page Mueller report are redacted, and House Democrats have for months fought to see them as part of their sweeping corruption probe into Trump and his associates.

Trump's responses drew new scrutiny last week during the criminal trial of Roger Stone. The longtime Republican political trickster and Trump ally was convicted on Friday of seven counts, including witness tampering and lying to Congress. The trial was centered around Stone's contacts with WikiLeaks, which during the 2016 presidential election published Democrats' internal emails that had been stolen by Russian agents.

Former Trump campaign aide Rick Gates testified that he recalled a July 2016 phone call between Stone and Trump, after which Trump said that "more information" from WikiLeaks would be coming.

Trump, in his written answers to Mueller, claimed: "I do not recall discussing WikiLeaks with him, nor do I recall being aware of Mr. Stone having discussed WikiLeaks with individuals associated with my campaign."

Asked about CNN's report, Trump's lawyer Jay Sekulow told CNBC: "Read the answers to questions. They speak for themselves."