For the past few weeks, there have been far too many reports that indicated banks with fraudulent mortgage documentation were going to get away with a rap on the knuckles. Looks like at least one state attorney general isn't going along with that plan:

Ohio's attorney general threw a wrench into the banking industry's push to quickly restart foreclosures by fixing faulty paperwork, and pressed them to modify mortgage loans.

In two letters released Friday, Attorney General Richard Cordray criticized a number of banks and loan-servicing companies, including Wells Fargo & Co.; Ally Financial Inc.'s GMAC Mortgage; Bank of America Corp.; and J.P. Morgan Chase & Co. Mr. Cordray said the banks are trying to paper over fraud committed in foreclosures with temporary fixes that don't address underlying problems in the banks' practices.

"It is not acceptable for a party who believes they submitted false court documents to merely replace those documents. Wells Fargo and any other banks are not simply allowed a 'do-over,' " he wrote in the letter to Wells. The other letter was sent to Ohio judges, who were asked to notify Mr. Cordray when banks file substitute affidavits.

He demanded that the banks vacate any court order or motion that was based on improper paperwork. In an interview Friday, Mr. Cordray said the banks would "be well-served to work out a settlement with the borrowers to modify the loans and work out payments."

Mr. Cordray's letters come as several banks say they have reviewed their foreclosure procedures and are resuming evictions. But his insistence that they go beyond replacing affidavits by employees who have been labeled "robo-signers"—who didn't adequately review underlying foreclosure documentation—threatens to upend banks' efforts to resolve their foreclosure problems.

Mr. Cordray's strategy gives clues to the goals of a 50-state probe, which was announced two weeks ago. Led by Iowa Attorney General Tom Miller, the effort was joined by top law-enforcement officers from all 50 states in response to reports of widespread errors in foreclosure filings and allegations of robo-signing.

"The banks are committing fraud on the court, essentially perjury, and then saying 'Whoops! You caught me! Here's some different evidence and use that instead,' " Mr. Cordray said in an interview Friday. "I know a lot of judges are not going to take kindly to that."

Bank of America declined to comment. A Wells Fargo spokeswoman said Friday the company intends to cooperate with Mr. Cordray's inquiries and doesn't "believe that any of these instances led to foreclosures which should not have otherwise occurred." She added that Wells Fargo has "chosen to submit supplemental affidavits out of an abundance of caution."