Washington (CNN) The federal government spent nearly $7 million investigating Russian meddling in the presidential election between May and September, the Justice Department announced Tuesday.

Special counsel Robert Mueller spent $3.2 million over that time.

Another $3.5 million has separately been spent by law enforcement personnel working on the investigation but who do not directly report to Mueller, DOJ said.

Mueller was appointed in May to lead the investigation into Russian meddling in the 2016 election.

The special counsel's budget includes some one-time costs, such as $734,000 for equipment that the Justice Department will keep once the investigation ends, the statement of expenditures said. Another $220,000 helped the special counsel's office employees relocate to work with Mueller.

The budget overview notes that its funding comes from a "permanent, indefinite" appropriation for independent counsels to do their work, meaning if cannot be touched by Congress. Some of the costs in the budget are for expenses the Justice Department would have already spent on other teams, such as for employees on detail to Mueller from other DOJ divisions. More than $1 million went to employees on detail.

Another $500,700 was paid to employees hired by Mueller from organizations outside of the Justice Department. Those people include Mueller himself, Jeannie Rhee, James Quarles and Aaron Zebley, who left the law firm Wilmer Hale with Mueller in May, and Greg Andres, the prosecutor who left the law firm Davis Polk in August and is co-leading the case against former Trump campaign chair Paul Manafort and his deputy Rick Gates. The private practice lawyers who joined Mueller's office each gave up more than a million dollars in annual pay, according to their previously reported financial disclosures.

The special counsel's investigation has focused on potential collusion between the Trump campaign and Russia, as well as obstruction of justice by President Donald Trump, who might have tried to impede the investigation. CNN reported that investigators are scrutinizing Trump and his associates' financial ties to Russia.

Mueller's team has also examined foreign lobbying conducted by Manafort, former national security adviser Michael Flynn and others.

His team has issued subpoenas for documents and testimony to a handful of figures, including some people close to Manafort, and others involved in the June 2016 Trump Tower meeting between Russians and campaign officials.

So far, Mueller has charged Flynn, Manafort, Gates and former campaign foreign policy adviser George Papadopoulos.

Democratic Sen. Dianne Feinstein of California praised the work done by Mueller and his team in a statement Tuesday.

"Special Counsel Mueller has spent $3.2 million on the first five months of his investigation, a figure that is entirely reasonable given the results we've already seen. With two individuals having entered guilty pleas and two more facing federal charges, it's clear the investigation is moving forward," she said in a statement. "I continue to strongly support Bob Mueller's investigation and believe he should receive all the resources he needs to follow the facts and the law where they lead."