(CNN) The House's impeachment inquiry is in full swing this week and investigators have several high-profile individuals from across the State Department, Pentagon and the Office of Management and Budget whom they plan to interview in closed-door depositions -- though when those depositions will happen remains in flux.

While the list of depositions started this week at seven, it was down to just two by Monday afternoon, though a third was rescheduled by Monday night. Only US embassy in Ukraine's charge d'affaires William Taylor and Deputy Assistant Secretary of Defense Laura Cooper remained on the schedule provided by an official working on the impeachment inquiry. The official cited memorial arrangements for the late Rep. Elijah Cummings, the chairman of the House Oversight Committee who died last week, for canceling previously scheduled depositions for Thursday and Friday.

A source familiar said Monday night that the deposition of acting Assistant Secretary for European and Eurasian Affairs Philip Reeker had been rescheduled for Saturday.

That followed acting OMB Director Russ Vought tweeting Monday morning that neither he nor associate director Michael Duffey would comply with the depositions requests. It's not clear at this time why other depositions scheduled for earlier in the week were postponed.

Here's who is on the agenda and who had their depositions postponed until further notice:

Charge d'affaires at the U.S. Embassy in Ukraine William Taylor speaks to the media during the briefing, in Kiev, Ukraine.

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