Just days before Ontario's ombudsman was to release a report about allegations of rigged lottery games and stolen jackpots, a shake-up happened in the executive offices of Ontario Lottery and Gaming.

The provincially-run lottery corporation's CEO resigned last week. OLG announced his departure Friday evening.

"By mutual agreement, Duncan Brown and the Board of OLG have decided a change of leadership is appropriate," a press release from the corporation said.

"Brown has stepped down from his post as CEO."

But a report published Saturday in the Toronto Star said Brown was "in shock" because he was planning to implement recommendations after the release of the ombudsman's report.

Brown had been steering OLG through turbulent waters after allegations of fraud and theft by lotto retailers were revealed.

Ombudsman Andre Marin launched an investigation into whether lottery retailers have won a disproportionate number of large prizes. His report is being tabled Monday and is expected to be critical of OLG.

Speaking with CTV NewsNet on Saturday, Marin would not be specific about his findings.

"As ombudsman, nothing I say is binding in the end. I only make recommendations. ... We'll see on Monday when I release the report what the government's reaction is," Marin said.

"I'm hoping, quite frankly, that all the recommendations will be accepted and implemented quickly," he added, noting that the provincial minister responsible for OLG has scheduled a press conference for Monday.

Last week, CTV News revealed that OLG was pulling more than three million "Super Bingo" scratch cards from the marketplace after a complaint that buyers could spot winning tickets without scratching.

There have also been accusations that ticket retailers were winning a disproportionate number of jackpots.

Opposition Leader John Tory called it all "a growing scandal." He questioned why OLG kept silent about Brown's departure.

"This corporation is out of control," Tory said.

Tory will be pressing for a deeper investigation into the lottery corporation.

"I think we're going to see from the ombudsman's report more evidence of that. Now the CEO is gone without any explanation as to why and with an attempt to cover up."

Brown, a well-respected lotto expert, has worked in the industry since the 1970s. He earned about $360,000 last year.

Marin said that the lottery in Ontario is "big business."

"We want to make sure that the trust in the system, the confidence, is protected and you know what, when you buy a ticket and you win the jackpot, you want to be able to pocket it," Marin said.

"So I'm hoping that the measures that we'll be recommending are able to address and make sure that the system better serves the people in Ontario."

With a report from CTV's Chris Eby and files from The Canadian Press