Officials of The Philadelphia Inquirer National Sudoku Championship have frozen payouts of the top prize awards from Saturday's finals pending an investigation of suspected cheating.

At the same time, questions multiplied about the man who registered for the tournament Saturday as a walk-in under the name Eugene Varshavsky.

After skipping the first round of puzzles, Varshavsky, wearing a hooded sweatshirt, blazed through the second round before floundering on the final championship puzzle. That was still good enough to bring him third place, worth $3,000, among 646 contestants.

Top competitors found his performance and his demeanor suspicious. After the competition, the blogosphere quickly began buzzing with skepticism and outrage. Chief among the bloggers was second-place finisher and former champion Thomas Snyder, who wrote competition officials a scathing "open letter" that went viral.

Tournament director Will Shortz and head of judging Nick Baxter raised questions in response to the concerns, and an investigation began Monday. Tournament officials declined to discuss suspicions of cheating.

Frozen are the nine top prizes awarded Saturday - three each in the beginner, intermediate, and advanced ranks. Tammy McLeod of Los Angeles won the grand prize, worth $10,000. Snyder took second place, at $4,000.

The $50 cash prizes for various age categories - from 10-and-under to 81-and-older - were presented to the winners on Saturday.

Varshavsky said when he registered that he was from Lawrenceville, N. J. There is no telephone listing for that full name, or even the last name, in that town. Varshavsky also told organizers that he worked for a company called Magic Crafts in Trenton. Attempts to find such a company have been unsuccessful.

A Eugene Varshavsky is registered at the social networking site LinkedIn, listing himself as a "Consultant for Magic Crafts" in "Electrical/Electronic Manufacturing." A second LinkedIn entry has him consulting for Magic Engineering L.L.C. of Brighton, Colo. Messages sent to both LinkedIn accounts have not been answered.

A man who identified himself as Eugene Varshavsky, an Israeli computer electronics engineer from Lawrenceville, came under suspicion at the World Chess Championships, held in Philadelphia in July 2006. According to various chess blogs, Varshavsky ranked far below the top 2,000 players in the world, yet beat several highly ranked players, including a grandmaster. It is virtually unknown for such a low-ranked player to improve at such a leap.

During the competition, Varshavsky wore a floppy hat that drew suspicion, and he eventually was searched. Although another man was expelled for cheating by electronic means, Varshavsky was allowed to finish. Monitored closely, he lost in the next round. In chess circles, the incident is known as the "Man in the Hat."

It is uncertain whether the chess Varshavsky is the Sudoku Varshavsky, or whether more than one person was involved in the activities now being investigated.

In both the chess and the Sudoku incidents, questions center on electronic cheating. Hand-held electronic devices such as iPods were allowed at the Philadelphia competition, drawing much criticism from the Sudoku community on the Internet.