NEW YORK (CNN/Money) - Federal and state authorities said Wednesday they are prosecuting at least 37 people who committed Internet fraud, mostly through the online auction site eBay.

Most of the violations involved sellers who, after taking buyers' money, failed to deliver high-quality "plasma" TV monitors, Sony PlayStations, computer parts and digital equipment, according to the Federal Trade Commission (FTC) and attorneys general from 29 states.

The Federal Trade Commission is launching a crackdown on Internet auction scams. CNN's Tim O'Brien reports from Washington. Play video (QuickTime, Real or Windows Media)

A California woman who pleaded guilty to four misdemeanors last year sold a counterfeit Louis Vuitton handbag. Others unloaded stolen merchandise. In addition, in some cases fake escrow accounts were used to steal buyers' funds. Some of the Internet deceptions, authorities said, occurred with the use of stolen identities.

But the majority of abuses involved people who collected money for goods they never delivered, in a sign that criminals are gravitating to one of the Internet's most profitable businesses: eBay.

"It's clear that what is going on here is outright fraud," said Howard Beales, who directs the FTC's Bureau of Consumer Protection. Beales said online auction-related complaints to the federal agency tripled to 51,000 last year.

Beales said eBay, the Web site where hundreds of thousands of buyers and sellers meet electronically to list and bid for goods, has cooperated in helping find and prosecute cases that resulted in 57 criminal and civil law enforcement actions. An eBay spokesman did not immediately return a call requesting comment.

Beales announced "Operation Bidder Beware" at a Washington news conference with Christine Gregoire, the attorney general of Washington state.

"All is not well with online auctions," said Gregoire, who said the most important protection consumers can take is to use credit cards rather than sending cash. "When you buy, be extra careful," she said. Credit card companies typically refund fees from transactions that turn out to be fraudulent.

Authorities recommend that online auction users not provide Social Security number, driver's license number, credit card number or bank account information until they have checked the legitimacy of the seller and the online payment or escrow service. Also, save all transaction information.

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Beales said complaints about online auctions, involving more then $40 million last year, led the list of all types of Internet fraud reported to the agency. The online auction market is dominated by eBay (EBAY: up $0.21 to $92.91, Research, Estimates), a profitable company that survived the Internet bust to prosper despite the sluggish economy.

eBay said this month that 2003 sales could top $2 billion, above forecasts by Wall Street analysts. Its stock is up 37 percent this year and remains near its 52-week high of about $95. The rise comes despite questions about whether shares of eBay, which trade at 64 times this year's earnings estimates, are overvalued.

The FTC alleges that in one case a defendant combined auction fraud while using stolen identities. In that case, the FTC charges that, since early 1999, the defendant constantly changed his Internet auction account name to conceal the fact he took payments before failing to deliver promised goods.

Elsewhere, the Orange County, California district attorney is bringing charges against a woman authorities say sold fraudulently obtained dental equipment.

One fraud involved Premier Escrow, which according to the FTC disguised itself as an independent escrow account meant to hold buyers' funds until the sale was completed. But Premier intercepted merchandise from sellers while taking money from buyers, the agency said. A Federal Court in Virginia has ordered a halt to the scam, dismantled Premier's Web site and frozen its assets, the FTC said.

But from Oregon, Wisconsin and Kentucky, it was failure to deliver -- football tickets by a New Jersey man, stereo equipment sold by a West Virginia man, for example -- that dominated the list.