House Financial Services Committee Chair Maxine Waters and Treasury Secretary Steve Mnuchin are set to clash again Wednesday morning as the fight over President Donald Trump’s tax returns continues to fester.

Mnuchin was scheduled to testify at 8:30 a.m. after an April session between the two got testy as they argued over when to end the questioning.

Waters also is expected to ask Mnuchin whether or not Trump instructed him not to hand over his tax returns.

The conflict is  part of a larger operation by House Democrats to investigate Trump and his finances, which the White House refuses to turn over because it says Democrats aren’t digging into them for any legitimate legislative purpose.

Mnuchin himself has refused to turn over six years of requested tax returns requested by House Ways and Means Chair Richard Neal, D-Mass., and the White House has instructed former White House Counsel Don McGahn and Attorney General Willaim Barr not to appear at scheduled hearings to answer questions.

In response to the Trump administration’s stonewalling, House Democrats are reportedly more serious about opening impeachment proceedings on the president.

After Mnuchin again refused to turn over Trump’s tax returns on Friday, Texas Democrat Lloyd Doggett called for Mnuchin to be arrested for “inherent contempt.”

House Speaker Nancy Pelosi also reportedly joked that “there is a little jail” on Capitol Hill for Mnuchin if needed.

Mnuchin has said the decision to withhold the highly sought-after tax returns is based on advice received from the Department of Justice.

The last time Waters questioned the Treasury Secretary things got heated when she asked him if he could give the committee another 15 minutes so members who had been waiting for their five-minute turn could ask him questions.

Mnuchin said it would be “embarrassing” if he kept a foreign leader waiting with whom he had a previously scheduled meeting.

He and Waters then sparred over whether Mnuchin would agree to come back in May to answer more questions.

Mnuchin said he had a list of appearances by other Treasury secretaries and that none of them had been forced to testify for more than three hours and 15 minutes. He said that when Republicans controlled the House, “they did not treat the secretary of the Treasury this way.”

Waters fired back: “This is a new day and it’s a new chair, and I have the gavel at this point. If you wish to leave, you may.”

That comment seemed to confuse Mnuchin, who did not know whether Waters was ending the hearing.

Mnuchin told Waters, “Please dismiss everybody. I believe you are supposed to take the gavel and bang it.”

Waters replied sharply, “Do not instruct me as to how I am to conduct this hearing.”

Editor’s note: More coming as today’s story develops.