A sweeping Auditor General’s audit of the Senate has cost taxpayers $21 million, and uncovered troubling expense claims from 10 more sitting and former senators, CTV News has learned.

The 10 senators filed questionable expenses amounting to more than $100,000, sources told CTV’s Ottawa Bureau Chief Robert Fife.

Just as the questionable spending of Mike Duffy, Pamela Wallin, Patrick Brazeau and Mac Harb were sent to the RCMP, sources say the latest cases will be, too.

“There are people who were saying, ‘Oh, there is just a couple of bad apples,” said NDP MP Paul Dewar. “Well, now it’s potentially 14. That’s a lot of apples.”

Just two weeks ago, Senate Speaker Leo Housakos vowed quick action, saying senators who have improper expenses will be referred to “other authorities.”

It’s not known how many of the 10 are sitting senators.

CTV has also learned that the sweeping investigation cost taxpayers $21 million, making it the most expensive audit ever conducted on Parliament Hill.

Sources say 142 auditors, many of them hired on contract from private firms, were given security passes for the Senate.

For the past two years, federal auditors combed through the expenses of 117 current and former senators.

“There are a lot of people who are hurting in this country and will be scratching their heads and going, ‘This is 2015 -- what the hell is going on?’” Dewar said.

The audit identified 30 additional senators who had problems with expense claims, including trips that did not appear to involve parliamentary business.

These expenditures are not enough to trigger an RCMP investigation, but the Senate will require them to re-pay money, sources say.

The auditor general’s office declined to comment on the findings until the report is released in the first week of June.

With a report by CTV’s Ottawa Bureau Chief Robert Fife