There are more than 4,000 Katrina-related registered websites, more than four times the number from last week, Louis Reigel, assistant director of the FBI's cyber division, said in statement posted on the FBI's web site Wednesday.
"Many of them may be legitimate, but fraudulent ones are popping up faster than we can pound them down," he said. "We're seeing more scams now than we saw after the Southeast Asian tsunami last December. The complaints started rolling in just a few days after Katrina made landfall."
Based on complaints it has received, the agency is investigating several fraudulent sites and also is working closely with the American Red Cross, which has been a primary target of the scams, he said.
The FBI also has partnered with the Justice Department, Federal Trade Commission, and other government agencies to form the Hurricane Katrina Fraud Task Force, he said.
Reigel advised people not to respond to unsolicited emails requesting donations. Those who want to donate should type in the web address of a recognized charity into a browser.