When Frank Johnston’s insurance carrier rejected his claim that flooding from Hurricane Sandy had severely damaged the foundation of his Fire Island home, the company cited an engineering report that seemed to establish his problems were “unrelated” to the storm, and were caused instead by the “long-term deterioration” of wooden piers beneath his house.

In reality, the original had reached the opposite conclusion. The engineering report, documents show, had been altered.

Mr. Johnston is part of a growing number of homeowners who suspect that their engineering reports were similarly rewritten as part of an effort to minimize insurance payments to flood victims in New York and New Jersey after the 2012 hurricane.

In November, allegations of altered reports prompted a federal judge overseeing more than 1,000 hurricane related lawsuits in the New York City area to order all drafts of the engineering reports be turned over, saying he believed such revisions could be “widespread.” Lawyers for homeowners in the suits began reviewing the documents, and say they have already identified more than 500 doctored reports.