OTTAWA -- The RCMP closed another chapter in the long-running Senate expense saga Thursday by declaring they won't charge Sen. Pamela Wallin after an extensive criminal review of her travel claims -- a probe some senators say went on too long.

The long-awaited announcement comes nearly three years after the RCMP first started looking at the Saskatchewan senator and a month after the sensational dismissal of 31 criminal charges against Sen. Mike Duffy.

The force has also closed its files on the majority of senators who were flagged with problematic expense claims in last year's report by the federal auditor general.

The statement from assistant commissioner Gilles Michaud said the "thorough investigation" of Wallin's expenses was over, and that Crown attorneys and investigators believed "no criminal charges will be laid."

As she walked out of the Senate chamber Thursday, Wallin expressed relief that the Mounties had finally made a decision.

"It has been a very long three years and I'm glad this nightmare is over," she said. She'll consult her lawyer about possible next steps, she added, but refused to elaborate on what those may be.

Fellow Saskatchewan senator David Tkachuk, who chaired the committee that oversaw Wallin's spending audit, said he never believed Wallin did anything criminal in her expenses.

Sen. Larry Campbell said he hoped the Crown dropped the fraud and breach of trust charges against Patrick Brazeau, whose trial is scheduled to start in June 2017 after he tried to end his life in January.

The Mounties opened a file on Wallin in 2013 after a critical audit of her spending ended with her repaying some $150,000 -- including interest -- for claims the Senate said were unjustified. The audit and subsequent investigation raised questions about whether Wallin was charging the Senate for travel related to her work on the various corporate boards on which she used to sit.

Among the claims were 24 events Wallin attended in her capacity as a member of the boards of Porter Airlines and Gluskin Sheff.

Wallin admitted she shouldn't have charged them to the Senate, pointing to what her lawyer called "administrative oversight."

When she paid the money back in September 2013, she blamed a "lynch mob" mentality in the Senate.

Two months later, Wallin was suspended without pay from the Senate in November 2013 over disallowed expenses, along with Duffy and Patrick Brazeau. The suspensions were lifted when Parliament was dissolved for the fall election.

Asked about Wallin's analogy, Sen. Jim Munson said the Senate acted "pretty close" to a mob in how it dealt with Wallin, convicting her before she had a fair hearing.

He also questioned how long it took the Mounties to settle her case.

"The wheels of justice in this case moved slower than ever. Nobody ever greased these wheels to say, 'Let's take a hard look at this,"' Munson said.

"To have your name out there in the lights and the rest of it, you're almost being convicted because your name is there. Why? Because you're a public figure."

Conservatives in the Senate said the upper chamber had every right to suspend the trio without pay, arguing it was a separate issue from the criminal investigations each one faced. Still, Sen. Don Plett, a close friend of Wallin's, said the upper chamber put "the cart before the horse" when they suspended her.

Former prime minister Stephen Harper appointed Wallin to the Senate in 2009, but Wallin left the Conservative caucus at the height of the expense scandal in 2013.