The White House and the State Department failed Friday to hand over documents related to probe by both chambers of Congress into President Donald Trump’s abrupt firing of State Department Inspector General Steve Linick.

Rep. Eliot Engel, D-N.Y., the chairman of the House Committee on Foreign Affairs, and Sen. Bob Menendez, D-N.J., the ranking member of the Senate Committee on Foreign Relations launched an investigation last week into Linick’s removal earlier this month and demanded that administration officials turn over all documents related to that firing by Friday, May 22.

A House Foreign Affairs Committee aide familiar with the probe told NBC News on Friday that no documents have been received by either committee.

“The White House and State Department failed to provide an adequate response to Saturday’s records request,” the aide said. “But pressure is building and the truth will come out.”

Congressional oversight officials investigating the matter believe the firing was direct retaliation for Linick pursuing an investigation into whether Secretary of State Mike Pompeo made a staffer walk his dog, pick up his dry cleaning and make dinner reservations for Pompeo and his wife, among other personal errands.

“President Trump’s unprecedented removal of Inspector General Linick is only his latest sacking of an inspector general, our government’s key independent watchdogs, from a federal agency. We unalterably oppose the politically-motivated firing of inspectors general and the President’s gutting of these critical positions,” wrote Engel and Menendez in the letter.

The officials said they are working to learn whether Linick may have had other ongoing investigations into Pompeo. The officials believe the staffer is a political appointee who was serving as a staff assistant. A White House official previously told NBC News that Pompeo “recommended” Linick’s ouster and that President Donald Trump agreed with the move.