WASHINGTON — Members of Congress are on recess for two weeks, but the impeachment inquiry into President Donald Trump appears to be steaming ahead.

The House Intelligence Committee, newly tasked with leading the investigation into the president’s dealings with Ukraine, will work through the time off, the committee's chairman, Adam Schiff, told reporters last week. Some members of the committee are expected to return to Capitol Hill during the break, as well, with at least one closed-door hearing set for the coming days.

On Monday, the Democratic chairmen of the Intelligence committee, House Foreign Affairs Committee and House Oversight Committee issued a subpoena to the president's lawyer, Rudy Giuliani, for documents related to Ukraine. The subpoena called on him to hand over the requested documents by Oct. 15. They also sent separate letters Monday and announced depositions for three of Giuliani's business associates.

Schiff said Sunday on NBC's "Meet the Press" that there was no set timetable for the probe, "except that we want to do this as urgently as possible." Appearing on ABC's "This Week," the California Democrat said multiple House committees involved in the impeachment inquiry were "moving forward with all speed" after having scheduled the depositions of five State Department officials over the next two weeks.

Those officials include the former U.S. ambassador to Ukraine, Marie Yovanovitch, who was abruptly ousted from her post in May, and the former U.S. special envoy to Ukraine, Kurt Volker, who resigned last week.

The committees set Yovanovitch's deposition for Wednesday, and Volker's for Thursday, though it remained unclear Monday whether either would appear.

"The failure of any of these Department employees to appear for their scheduled depositions shall constitute evidence of obstruction of the House's impeachment inquiry," the three top Democratic House chairmen — Schiff, Foreign Affairs Committee Chairman Eliot Engel and House Oversight Committee Chairman Elijah Cummings — wrote Friday in a letter to Secretary of State Mike Pompeo.

Pompeo, meanwhile, faces an Oct. 4 deadline to turn over documents related to Trump's July 25 call with Ukrainian President Volodymyr Zelenskiy subpoenaed by the chairmen.

Also on Oct. 4, the inspector general for the intelligence community, Michael Atkinson, is set to testify in a closed-door hearing before the Intelligence committee, which Schiff said in a letter Friday is “critical to establish additional details, leads and evidence.”

In a conference call with members of the House Democratic caucus Sunday afternoon, House Speaker Nancy Pelosi and other Democratic leaders underscored the serious nature of impeachment and delivered a messaging game plan as members prepare to spend extended time in their districts, according to multiple sources on the call.

Caucus Chair Hakeem Jeffries of New York summarized the message in six words: "Betrayal, abuse of power, national security."

Schiff also said on "Meet the Press" Sunday that he hopes to have the intelligence community whistleblower whose complaint fueled the House impeachment inquiry testify before his panel "very soon."

“All that needs to be done, at this point, is to make sure that the attorneys that represent the whistleblower get the clearances that they need to be able to accompany the whistleblower to testimony, and that we figure out the logistics to make sure that we protect the identity of the whistleblower,” he said.

An attorney for the unidentified whistleblower, Mark Zaid, confirmed in a statement Sunday that discussions with Congress were ongoing, and no date or time had been set for an interview. The whistleblower's legal team has raised "serious concerns" that Trump's critical comments have put their client in danger.

The whistleblower’s complaint, released to the public on Thursday, alleged that in a July phone call with the president of Ukraine, Trump used the power of his office “to solicit interference from a foreign country" in the 2020 election. The whistleblower also alleged that the White House tried to “lock down” all records of the call between the two leaders because officials understood the gravity and potential consequences of what had transpired during the conversation.

The president, in response, has taken aim not only at the whistleblower’s credibility but also at Schiff, suggesting in a tweet Monday morning that he should be arrested for treason.