The special counsel's office spent $3.2 million in its first four months probing ties between President Donald Trump 's top advisors and Russia, according to a release issued Tuesday by the Department of Justice .
The greatest expense was for the temporary reassignment of Justice Department employees, the report said, which totaled $1.2 million in the period. Payrolls for special counsel employees totaled about $500,000.
The expenses are those incurred between the May 17 appointment of Robert Mueller as special counsel and Sept. 30.
The special prosecutor's investigation of President Richard Nixon during the Watergate scandal cost about $16.5 million in inflation-adjusted dollars, according to data made available by The Nixon Library and Museum. That amounts to more than $3 million a month between the appointment of special prosecutor Archibald Cox in May 1973 and his firing in the "Saturday Night Massacre" on Oct. 20 of that year.
The Whitewater investigation, which lasted much longer, was more costly. The independent counsel spent more than $60 million over the course of that six-year inquiry into then-President Bill Clinton. Spending on the probe escalated rapidly as the investigation concluded, Government Accountability Office figures showed at the time.
It is likely that Mueller's investigation could last for years, according to an analysis of previous special counsel probes conducted by the data analysis website FiveThirtyEight.
That analysis also found that Mueller 's investigation is accelerating more rapidly than previous inquiries. On average, according to FiveThirtyEight, previous special counsel investigations that have filed criminal charges have taken more than a year to do so.
Mueller's investigation has already charged four individuals with criminal wrongdoing. Two have pleaded guilty.
The special counsel spent more than $700,000 acquiring equipment, according to the filing. It noted that the equipment would remain the property of the government at the end of the investigation.
Among other expenses included in the filing are $111,245 spent on IT services, $24,456 on transcripts and $867 on "Investigative Reports/Information."
Read the special counsel's full expense report: