Putting more pressure on insurers to pay damage claims from Hurricane Katrina, Mississippi's insurance commissioner has told carriers that they will be required to prove to both regulators and homeowners that damage was caused by water and not by wind if they deny a claim.

On Wednesday, Lousiana's insurance commissioner also urged a large group of insurers and reinsurers to pay all valid claims. In many cases, the key to deciding which homeowners recover will be whether wind or water caused the damage.

Many homeowners' and business insurance policies exclude flood damage from their coverage. Flood coverage is written by the federal government through its National Flood Insurance Program, but only a small fraction of property owners in Mississippi and Alabama have bought it.

"In some situations, there is either very little or nothing left of the insured structure, and it will be a fact issue whether the loss was caused by wind or water," Mississippi Insurance Commissioner George Dale said in a bulletin to insurers dated Wednesday. " . . . I expect and believe that, where there is any doubt, that doubt will be resolved in favor of finding coverage on behalf of the insured."

Dale's position startled many insurers and reinsurers, who are concerned they are being pressured to pay claims for damage they did not insure.

Even in Florida, with its many hurricanes, regulators "haven't ever tried to do that," said Brad Kading of the Reinsurance Association of America.

Some industry officials said they did not view Dale's action as alarming.

"I think this is just a cautionary bulletin to lay out what his expectations are," said Julie Pulliam of the Atlanta office of the American Insurance Association, a trade group. "He has been very good to work with, and we expect that to continue. We are at the very beginning of this process. There's a lot to come."

Telephone calls to the Mississippi Insurance Department did not go through, apparently because of damaged phone lines and a high volume of calls to the area.

Kading and others said that at a meeting convened Wednesday by Louisiana Insurance Commissioner J. Robert Wooley to discuss dealing with the disaster regulators were largely hortatory. Kading said they made "no specific draconian statements."

Nonetheless, both insurers and reinsurers are alarmed at the idea of being forced to pay flood claims, as some have urged.

The industry notes that flood exclusions are long established and that the language in policies is approved and understood by regulators. More important from a financial standpoint is that if insurers pay flood claims, reinsurers' contracts typically allow them to refuse to reimburse insurers for those outlays.

"The reinsurer is in the position of indemnifying the insurer," Kading said. That means that "after paying a claim, the insurer presents evidence that it was covered [by the reinsurance contract], and proof that it was paid. The reinsurer then looks at that evidence and decides if it agrees it's a covered claim."

By some estimates, reinsurers will pay about 40 percent of insured losses from Katrina and primary carriers the rest, assuming normal treatment of flood losses. If insurers pay claims that the reinsurers reject, their efforts to spread their risk will be negated, perhaps threatening their solvency.

But much remains uncertain with regard to losses, irrespective of who pays them. "We are still totally in an assessment-type mode, of how much and where," said John Marlow of the AIA's southwestern regional office in Austin.

Insurance chief George Dale wants to protect Mississippi claimants.

Connie Kate tries to salvage belongings from her house that was flattened by Hurricane Katrina in Gulfport, Miss. The state insurance chief urged insurers to pay claims.