In December, British Customs agents at London's Heathrow Airport intercepted a package of pre-addressed envelopes containing $226,000 worth of phony cashier's checks shipped from Nigeria and bound for "Ken Smith" in North Versailles.

The intercept was part of "Operation Tidalwave," an international crackdown on Nigerian con artists who have been ripping off Americans for 20 years using versions of the "Nigerian 419" or "advance fee" scam. The number comes from a section of the Nigerian penal code.

Ken Smith, it turns out, was really Adebayo Adedimila, 29, an American citizen holding a Nigerian passport.

Agents arrested him last month, and Wednesday, a federal grand jury indicted him on mail fraud charges in connection with a counterfeit check scheme that represents the latest mutation of the 419.

"A similar Nigerian scheme has been operating since the early 1980s and originally used unsolicited letters and faxes sent to businesses," said U.S. Attorney Mary Beth Buchanan in a statement. "However, with the increasing popularity of e-mail and the expansion of the Internet, variations on the fraud have become increasingly creative and virtually endless."

Buchanan highlighted the case as part of National Consumer Protection Awareness Week, which started Monday.

The Adedimila arrest is the latest in a new wave of enforcement targeting Nigerian scam artists both in Nigeria and in the Western nations from which they draw their victims.

The U.S. Secret Service has made some 250 arrests in Nigeria in recent years. Last month, Dutch police rounded up 52 suspects in Amsterdam, accusing them of pulling a version of the 419 in which scam artists send spam e-mails asking for help in transferring millions of dollars from an African nation in exchange for a percentage.

The Adedimila case involves a newer scheme using Internet auction sites such as eBay to entice the gullible into parting with a few thousand dollars.

Typically, a Nigerian will contact a seller and say he has a "friend" in the United States who owes him money. He says the friend will send the seller a cashier's check to cover the cost of the item being sold. But the check is for more than the item is worth.

The Nigerian ships the phony cashier's check to a cohort in the United States -- Adedimila's role, federal agents say -- who sends it to the unsuspecting seller through the U.S. mail.

Finally, the buyer asks the seller to send back the extra money by Western Union wire.

"Often, the sellers act as requested and wire the additional funds prior to the cashier's check being returned as counterfeit to the seller's bank," said Postal Inspector Joseph Bell, in a search warrant affidavit for Adedimila's apartment. "This scheme has affected thousands of victims across the United States and resulted in the loss of millions of dollars."

In Adedimila's case, someone identifying himself as "David Nelson" sent e-mails to the sellers saying he wanted to buy.

Nelson then told them that he had a client -- "Ken Smith" -- in the United States who owed him money and would send the seller a cashier's check. He said the amount of the check would be more than the cost of the item. Nelson told the sellers to cash the check and wire the excess funds to a destination he chose.

After negotiating this deal with 20 potential victims, Nelson shipped the checks in the name of "Ken Smith" to Adedimila's apartment. After Customs intercepted the package, U.S. postal inspectors set up a sting in which one of them posed as a United Parcel Service deliveryman.

Adedimila was arrested Jan. 2 at his apartment in North Versailles.

On Jan. 8, a second package of pre-addressed envelopes and counterfeit checks arrived at the apartment from Nigeria, but by that time Adedimila had been arraigned and released to a friend in Turtle Creek.

Prosecutors won't say if they have identified or arrested "David Nelson" in Nigeria.