The State Department's entire senior level of management officials resigned Wednesday.
Patrick Kennedy, the agency's undersecretary for management who had served in the role for nine years, resigned unexpectedly along with three of his top officials.
Assistant Secretary of State for Administration Joyce Anne Barr, Assistant Secretary of State for Consular Affairs Michele Bond and Ambassador Gentry O. Smith, director of the Office of Foreign Missions, resigned as well, the report said.
All of them served under both Democratic and Republican administrations.
They join a number of other officials who have departed since President Trump took office last week.
Assistant Secretary of State for Diplomatic Security Gregory Starr retired, and director of the Bureau of Overseas Building Operations Lydia Muniz left on Friday.
"It's the single biggest simultaneous departure of institutional memory that anyone can remember, and that's incredibly difficult to replicate," said David Wade, who served as State Department chief of staff under Secretary of State John Kerry.
"Department expertise in security, management, administrative and consular positions in particular are very difficult to replicate and particularly difficult to find in the private sector."
President Trump's nominee for secretary of State, former Exxon Mobil CEO Rex Tillerson, was reportedly at the State Department headquarters on Wednesday. At the time, the Trump team was looking to hire Tillerson's No. 2 and three other officials as well as replace Kennedy.
Earlier this week, Senate Majority Leader Mitch McConnell (R-KY) said he was moving the Senate toward a vote on Tillerson.
"I'll be filing cloture on secretary of State nominee Tillerson, which will ripen next week," McConnell told reporters during a weekly press conference.
The move would set up a procedural vote early next week and get Tillerson through the Senate by the end of the week. Democrats have been lining up against Tillerson, voicing concerns about his ties to Russia and positions on human rights.