Interim Chief of Staff Darrel Thompson said Friday that he was temporarily detailed three weeks ago to serve as Burris' chief of staff and the role has ended.
It was not immediately clear who will replace Thompson.
Thompson says he's going back to work as a senior adviser to Senate Majority Leader Harry Reid.
Burris is under pressure to resign from the Senate for not disclosing contacts with advisers to former Gov. Rod Blagojevich. Blagojevich appointed Burris to the seat before being impeached and ousted over corruption allegations.
The White House has said Burris should think about his future. Illinois Gov. Pat Quinn has called on Burris to quit.
