Special Counsel Robert Mueller is working on operation budget for probe

Special Counsel Robert Mueller is working on an operation budget for his investigation into Russia's interference in the 2016 U.S. election, reports CBS News' Paula Reid.

The size of the staff has not yet been determined. The money to fund the investigation will come out of the government's "permanent indefinite appropriation" fund which is allocated specifically to pay for all necessary expenses of investigations and prosecutions by independent counsels.

Mueller will submit his budget to the Justice Department's Assistant Attorney General for Administration Lee Lofthus. Lofthus says there is no real limit, and Mueller will get any funds he deems necessary, subject to the approval of the deputy attorney general.

The special counsel already has an office space in downtown Washington, D.C., and he has been cleared of any ethics conflicts.

Deputy Attorney General Rod Rosenstein appointed Mueller, the former FBI director, as special counsel last week.

"I have determined that a Special Counsel is necessary in order for the American people to have full confidence in the outcome," Rosenstein said in a statement.