Federal officials have warned promoters of more than 140 products sold over the Internet about fraudulent claims that they can prevent, treat or diagnose swine flu.

Bogus products include devices and sprays that claim to sterilize the air or surfaces, and dietary supplements claiming to boost the immune system. The U.S. Food and Drug Administration says it even has found fake Tamiflu being sold online without a prescription.

Officials say the problem has grown in recent weeks as vaccine is delayed and real Tamiflu continues to be reserved for only the sickest flu patients.

Fraudulent products emerged shortly after swine flu did last spring -- about 10 a day, said Alyson Saben, head of a swine flu consumer fraud team the U.S. Food and Drug Administration formed. That slowed over the summer as the flu abated, but lately "we are seeing new sites pop up," she said.

Most worrisome: sites claiming to sell Tamiflu directly to consumers. The FDA bought and tested five such products. One contained powdered talc and generic Tylenol -- no Tamiflu. Several others contained some Tamiflu but were not approved for sale in the U.S.

"We have no idea of the conditions under which they were manufactured. They could contain contaminated, counterfeit, impure or subpotent or superpotent ingredients," Saben said.

Tamiflu and Relenza are the only drugs recommended for treating swine flu.