Homeowners who suspect they were underpaid on flood insurance claims after superstorm Sandy have until Thursday to appeal their settlements to the Federal Emergency Management Agency.

FEMA has set a midnight deadline Thursday for storm victims to register online for the agency's review process, launched in May after homeowners accused private companies hired by the federal government of forging documents to deny settlements. To request a claim review, homeowners can visit fema.gov.

Storm victims can also register until 8 p.m. by calling 866-337-4262.

After a brief interview, FEMA will give homeowners two weeks to submit documents proving they were underpaid. If homeowners don't have receipts, the agency will accept sworn statements for expenses up to $7,500 per claim.

FEMA estimates the process will take up to 90 days. If homeowners disagree with the outcome, they can appeal to a panel of retired judges hired by FEMA to arbitrate the process. The agency, however, will have the final say.

So far, roughly 16,400 homeowners have signed up to have their claims reviewed, or about 12 percent of the 142,000 eligible.

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After completing the first roughly 700 reviews, FEMA found that 65 percent of homeowners were underpaid by an average of about $16,000.

The allegations of intentional underpayments have led to a criminal probe and the departure of two top flood insurance officials.

FEMA plans to spend roughly $40 million -- not including payments to homeowners -- to run the sweeping process, saying it's critical to restore the program's credibility.