U.S. officials and consumer advocates said they had not yet heard of any cases of identity theft related to the disaster because the crime usually takes months to unfold.
But consumers should keep a close eye on their bank statements and order a copy of their credit reports once they get their lives back together to make sure they are not being victimized, they said.
"We tell people not to be alarmed but to be cautious," said Betsy Broder, an assistant director in the Federal Trade Commission's Bureau of Consumer Protection.
Those who wish to contribute to relief efforts are at risk, as well. Internet security company Websense said on Sunday that it had found a "phishing" e-mail campaign that seeks to trick Internet users into providing their credit card numbers to a Web site that looks like one run by the Red Cross.
In order to avoid such scams, donors should type the address of charitable Web sites directly into their browsers, rather than clicking on a link in the e-mail, experts said.
The FBI is investigating at least a dozen suspicious Web sites and e-mail messages for fraud, spokesman Paul Bresson said.
emerged after the tsunami that devastated large portions of coastal Asia and Africa in December, but "this is far worse," he said.
The U.S. Department of Justice said on Thursday that it has set up a task force to investigate identity theft and other types of fraud related to Katrina.
Identity theft costs U.S. consumers and businesses $50 billion annually, according to FTC estimates.
A string of computer breaches at businesses and universities has focused attention on the issue this year, but those who have been uprooted by Hurricane Katrina also face risk from looters and "dumpster divers"--those who sift through garbage looking for valuable personal information to steal.
Ruined homes and businesses are likely to contain mortgage records, Social Security cards and other documents that criminals can use to hijack an identity, said Linda Foley, co-executive director of the Identity Theft Resource Center.
"A crisis brings out the best of people and the worst of people," she said. "Unfortunately, in criminals it brings out their best skills."
Thieves also could intercept drivers' licenses and birth certificates when they are mailed to storm victims trying to get their lives back together, said Beth Givens, director of the Privacy Rights Clearinghouse.
"I suspect that many of the shelters are temporary facilities, and do the people running them have the ability to operate a secure post office?" she asked.
Mail bound for the affected areas is currently held in secure sorting facilities and will be forwarded to residents once they fill out a change-of-address form, U.S. Postal Service spokesman Bob Anderson said.