The total cost of the federal investigation into Russian interference in the U.S. election over the first four and a half months of special counsel Robert Mueller’s investigation is over $6.7 million, according to the first public accounting of the probe.

Mueller’s office spent just over $3.2 million from the date his appointment, May 17, through Sept. 30.

The bulk of the expenses went toward staff, with $1.7 million spent on salaries and benefits. The special counsel has hired 17 attorneys to date to work on the probe.

Just over $220,000 was spent on travel during that period, while $156 went to a mysterious line item: “Transportation of things.”