(CNN) Federal prosecutors in New York have advanced their investigation into President Donald Trump's personal attorney Rudy Giuliani, pursuing more documents and witness testimonies while the Justice Department simultaneously accepts information from the former New York mayor on Ukraine, according to The Washington Post.

Citing people familiar with prosecutors' activities, the paper reported Friday that the department has been looking into Giuliani's business dealings as well as those of his indicted associates Lev Parnas and Igor Fruman throughout the final steps of Trump's Senate impeachment trial earlier this month, including witness interviews as recently as last week.

Attorney General William Barr on Monday confirmed that the Justice Department has been receiving information from Giuliani on Ukraine , saying the department has an "obligation to have an open door to anybody who wishes to provide us information that they think is relevant." He added there's skepticism about anything coming from Ukraine, which has prompted the department to establish an "intake process in the field" so the department and intelligence community can scrutinize Ukraine information.

The Ukraine allegations that Giuliani is providing to the Justice Department are being vetted by investigators in the US Attorney's Office in Pittsburgh, two US law enforcement officials told CNN on Tuesday. The officials told CNN that the Pittsburgh office has expertise on Russia and its cyber operations, including the 2016 disinformation campaign the Russians carried out.

Meanwhile, prosecutors in the investigation into Giuliani have pursued details on Marie Yovanovitch, the former US ambassador to Ukraine who Giuliani, Parnas and Fruman conspired to have removed, a person familiar with the request told the Post. A source familiar with the matter confirmed that Yovanovitch's name has appeared on a recent subpoena from Southern District of New York prosecutors that inquires about Giuliani and Parnas.

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