GILA RIVER INDIAN COMMUNITY, Ariz. (AP) -- Casino officials know how the big winner was dressed and when he played the slots. The problem is, they have no idea who walked away from the $38,000 jackpot.

Casino videotapes can't identify the man who hit it big on June 12. The way the man's head is positioned and the fact that he wore a hat has obscured the winner's face.

That hasn't stopped dozens of wannabe winners from calling in to claim they are the mystery man who won the casino's largest unclaimed jackpot.

"Everybody in the world is called saying `That's me," said Sheila Morago, marketing director at the Gila River Casino. "They're coming in all hours of the day."

All would-be claimants have to pass a quiz dealing with such factors as what time the winner was there and what he was wearing in an attempt to give the money to its rightful winner.

"We're not going to ask a trick question no one could answer," Morago said.

Why the man failed to claim the jackpot is itself a mystery.

"The bells and whistles went off," Morago said Monday. "The machine locked up like it was supposed to do, and the guy just walked away."

The casino plans to have the surveillance video digitally enhanced to help in the identification.