The House Judiciary committee has demanded that Attorney General William Barr hands over any messages President Donald Trump sent about the sentencing of his longtime friend Roger Stone, and also requested interviews with the four career prosecutors who quit the case after the president intervened to demand a lighter jail sentence.

In a letter released Friday morning, committee chairman Rep. Jerry Nadler made the urgent request to Barr and said that recent events at the Department of Justice were “deeply troubling.” Nadler urged Barr to hand over any communications showing “improper political interference, including by President Trump” in a string of recent cases.

Nadler asked that Barr make available for interview 15 different current and former officials, including the four career prosecutors—Aaron Zelinsky, Adam Jed, Jonathan Kravis, and Michael Marando—who quit the Stone case after Department of Justice headquarters stepped in to override their recommended prison sentence and push for a shorter term.

The prosecutors told a federal judge earlier this month to sentence Stone to seven to nine years in prison for lying to Congress, witness tampering, and obstructing a congressional probe into Russian interference in the 2016 election. After some very angry Trump tweets, the DoJ announced it would override that recommendation—and a federal judge eventually sentenced the Republican operative to 40 months in prison.

As well as asking for copies of any communications between Trump and White House officials related to the Stone case, Nadler made the same request of two other high profile interventions: the softening of ex Trump National Security Adviser Michael Flynn’s sentencing recommendation, and the overruling of a decision to send former Trump Campaign Chairman Paul Manafort to the notoriously brutal Riker’s Island prison.

Nadler also requested a list of all the occasions on which senior DOJ officials had intervened in sentencing in the past 10 years. He conceded that “the Department typically does not provide information regarding ongoing matters,” so doesn’t appear hopeful Barr will play ball.

Barr is reportedly scheduled to testify before the Judiciary Committee on March 31, but Nadler asked for a response by March 13.