OSAKA -- Around 70 counterfeit 5,000 yen bills bearing the same serial number have been discovered in Osaka Prefecture this year, police said Saturday.

On Tuesday, one of the fake 5,000 yen bills was found in a cash register at a Matsuzakaya Co. department store in the city of Osaka, police said.

The fake bills, bearing the serial number BG638851Z, do not have any built-in identification marks or watermarks but do have watermark-like designs apparently made with oil, police said.

The counterfeit bills are slightly smaller than genuine bills and appear to have been made with a personal computer and scanner.

Counterfeit notes with the same serial number have also been found in other parts of western Japan, they said, including one 5,000 yen bill found in September in Ehime Prefecture, according to police.