Mark Esper, U.S. Secretary of Defense, attends a welcoming ceremony for joint chiefs of staff Chairman Mark Milley at Fort Myer in Arlington, Virginia.

The leaders of three House committees on Monday announced they have subpoenaed the Pentagon and the Office of Management and Budget for documents related to the impeachment inquiry into President Donald Trump.

The Democratic chairmen of the House Intelligence, Foreign Affairs and Oversight committees are demanding a slew of documents related to Trump's request for Ukraine's president to investigate former Vice President Joe Biden and his son, as well as the Trump administration's decision to delay military aid to Ukraine.

The subpoenas were issued to Defense Secretary Mark Esper and the OMB's acting director, Russell Vought. They have until Oct. 15 to comply, according to letters sent by the committee leaders Monday.

Defense Department spokeswoman Jessica Maxwell said in a statement to CNBC that the department has issued an internal directive to retain documents related to the issue of aid to Ukraine.

"Last week the Department proactively issued an internal directive to retain documents related to this issue. As we've stated previously, we are prepared to work with Congress and other relevant parties on questions related to the issue of Ukrainian aid as appropriate," Maxwell said.

Spokespersons for the OMB and the White House did not respond to CNBC's requests for comment on the subpoenas.

"The Committees are investigating the extent to which President Trump jeopardized U.S. national security by pressing Ukraine to interfere with our 2020 election and by withholding military assistance provided by Congress to help Ukraine counter Russian aggression, as well as any efforts to cover up these matters," the leaders said in the letters to Esper and Vought.

Last Friday evening, those same Democratic committee leaders — Reps. Adam Schiff of Intelligence, Elijah Cummings of Oversight and Eliot Engel of Foreign Affairs — subpoenaed the White House itself for documents related to the impeachment probe. The White House has until Oct. 18 to comply with that subpoena.

Secretary of State Mike Pompeo and Trump's personal attorney, former New York Mayor Rudy Giuliani, have also been subpoenaed as part of the impeachment inquiry. Vice President Mike Pence has been issued a request for documents, as well.

House Speaker Nancy Pelosi announced the impeachment inquiry last month, on the heels of reporting about a whistleblower complaint that raised fears that Trump, in a July 25 call with Ukrainian President Volodymyr Zelensky, was "using the power of his office to solicit interference from a foreign country in the 2020 U.S. election."

The whistleblower's complaint, as well as a five-page memorandum of the call, were made public shortly after Pelosi announced the impeachment inquiry.

In that partial transcript, Trump asks Zelensky if he can "look into" unsubstantiated allegations that Biden pressured Ukraine to fire a prosecutor there in order to protect his son Hunter, who was on the board of a Ukrainian natural gas company while his father was Barack Obama's vice president.

There is no clear evidence suggesting that Biden wanted Ukraine to fire the prosecutor for personal gain. Many other world leaders had also called on Ukraine to fire that prosecutor, who was widely accused of corruption.

Democrats have also raised suspicions about the Trump administration's decision to withhold hundreds of millions of dollars in military aid to Ukraine that had been allocated by Congress, without providing a clear explanation for why the money was being held up. The aid was eventually granted to Ukraine, after months of delay.

Trump has recently said he made the decision to withhold that aid because he wanted other countries to pay a larger share of the assistance going to Ukraine. He has maintained that there was no "quid pro quo" tying the aid to his requests to Zelensky.

Text messages shared with Congress by former U.S. special envoy to Ukraine Kurt Volker, who testified behind closed doors last week, showed U.S. officials explicitly linking a probe of Trump's political opponents with Zelensky being granted a White House visit.

— CNBC's Dan Mangan contributed to this report.