OLYMPIA — A Senate panel Tuesday allocated an additional $75,000 to an investigator hired to help that chamber with its inquiry into the erroneous early release of prisoners in Washington state.

The money approved in an early morning 4-3 vote by the Facilities and Operations Committee is on top of the $50,000 cap the committee initially set last month, when the committee approved the hiring of Mark Bartlett, a partner at the firm of Davis Wright Tremaine. The cost of the Senate probe now exceeds the $110,000 spent on the two former federal prosecutors hired by Democratic Gov. Jay Inslee for the separate investigation he began in late December.

In a letter to the committee, Republican Sens. Mike Padden and Steve O’Ban said that Bartlett and his attorneys have interviewed at least 25 people and have reviewed more than 70,000 pages of documents.

“Because we are utilizing a different process than the Governor, we can allow the press and public to see for themselves key personnel testify under oath,” they wrote. “The press and public can then form their own judgments, rather than just accept conclusions by lawyers arrived at behind closed doors.”

The move by Senate Republicans comes a day after the Senate Law and Justice Committee held its first formal hearing on the software coding error that led to the early release of up to 3,200 prisoners since 2002 because of miscalculated sentences. At least two deaths have been tied to the early releases.

On Monday, Inslee notified the chairman of the Senate Law and Justice Committee that his investigation was complete and would be made public later this week.

“From my perspective it would have been dramatically better to have the governor’s investigators come present their findings to us and then ask Mr. Bartlett if we were going to engage a separate investigation to look and try to identify what gaps there might be and focus our resources on that rather than inventing the wheel for the third time,” Democratic Sen. Jamie Pedersen said after Monday’s hearing.

But in their letter to the committee, Padden and O’Ban argued that rather than wait for the details of the governor’s investigation to be made public, the money for the Senate investigator allows the committee “to do a full, independent investigation in a timely manner.”