Chicago billionaire Neil Bluhm is pouring more money into the Rivers Casino.

Mr. Bluhm, who rescued the project from near bankruptcy in 2008, is among a group of existing investors that plowed another $108 million into the casino in a bid to firm up its financial footing.

The casino also restructured debt to address financial concerns and credit downgrades precipitated by lower-than-expected slots revenues at the North Shore venue.

In an announcement Wednesday, the casino said the recapitalization would reduce its senior debt by more than 45 percent and result in "improved financial stability."

"We've got much lower debt payments, we've got more equity and our business is growing. We wouldn't make the investment if we didn't think it was a good investment," Rivers CEO Greg Carlin said.

Each of two groups of existing investors will contribute $54 million in new money to the project.

One group includes gambling affiliates of Mr. Bluhm, the Rivers chairman, and Walton Street Capital, a company he co-founded. The other is made up of the Detroit general retirement system and the Detroit police and fire retirement system.

An ownership group led by Mr. Bluhm took over the casino two years ago after Detroit businessman Don Barden failed to secure permanent funding for the project and defaulted on a $200 million loan used to start construction. As part of that deal, Mr. Bluhm's group put $205 million in cash into the project.

Mr. Carlin said the newest infusion of money would be used to buy back some of the casino's debt, pay the state-required $16.5 million licensing fee for table games, and help to fund capital improvements.

But the moves failed to impress one New York rating agency that has raised concerns about the casino's ability to meet debt service payments and other obligations, including the $7.5 million annual contribution to help pay for the new arena, based on the slots revenues it was generating.

In an update released hours after the Rivers announcement, Standard & Poor's downgraded the rating of casino affiliate Holdings Gaming Borrower from CCC to SD, or selective default. It marked the third downgrade since the casino opened in last August.

Standard & Poor's stated it viewed the buy back of some of the senior debt and the accompanying restructuring of other obligations as "tantamount to a default," given the "distressed financial condition" of the company.

The rating agency said it still had concerns about whether the moves would be enough to enable the casino to meet debt and other obligations in the future given its current operating performance.

Michael Listner, an associate director at Standard & Poor's, said the casino generated about $20 million in revenue last month, which he described as "somewhat low" given the size of the property, its $800 million cost, and the debt it was carrying.

Standard & Poor's had projected that the casino would generate an average win of $300 a day per slot machine. While the casino's revenues have improved markedly in recent months, they haven't come close to that. Even in the Rivers' best week of revenue since opening Aug. 9, the average win per machine was $251.

Despite Wednesday's downgrade, Standard & Poor's plans to do a more detailed analysis of the restructuring over the next few days and could return the rating to CCC with a negative outlook, Mr. Listner said.

In April, Moody's Investors Service also had downgraded the credit rating of Holdings Gaming Borrower from Caa2 to Caa3 because of similar concerns about operating performance.

Mr. Carlin couldn't be reached after Standard & Poor's released its statement, but he said in the earlier interview the additional investment and restructuring "certainly had improved the [casino's] capital structure by a significant amount."

"Our debt service will drop substantially. We should have cash flow to invest in the property. We're looking at building out function space, spending money on table games," he said.

"We wouldn't be investing all this money if we didn't think we were fixing our capital structure, if you will."

Mr. Carlin said he believes the introduction of table games, which are expected to start in July, should help to boost the Rivers' overall revenues, including those for slots.

The casino had projected that it would hit $427.8 million in gross terminal revenue in its first year of operation. Mr. Carlin said he believes the casino eventually will get there.

"I think what was optimistic was our ramp-up period. We expected a short ramp-up period. It's taken a little longer," he said. "With table games, I think we eventually will hit those numbers."

The infusion of capital and restructuring of debt, he added, "clearly demonstrates our commitment to Rivers Casino and the city of Pittsburgh, and our players should take comfort in the fact that we're willing to make a significant new investment in the property."

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