Officials of The Philadelphia Inquirer National Sudoku Championship are investigating suspicions of cheating in the finals of Saturday's tournament at the Convention Center.

The focus is on Eugene Varshavsky of Lawrenceville, N.J., who placed third out of 646 competitors and took the $3,000 third-place prize.

Varshavsky could not be reached by phone last night for comment. No Varshavsky is listed in the Lawrenceville telephone directory.

(Tammy McLeod of Los Angeles took the $10,000 first prize. Final puzzle results appear on Page D5 of today's Inquirer.)

Varshavsky, playing in a hooded sweatshirt, registered as a walk-on contestant Saturday morning, blazed through the second round in world-class time, but was unable to complete the easy first steps in the championship puzzle.

Other competitors, including former winner (and Saturday's second-place finisher) Thomas Snyder, saw that pattern as a red flag. Questions quickly arose in the Sudoku community and the blogosphere.

Tournament spokesman Jay Devine said in a statement that tournament director Will Shortz and Nick Baxter, the head of judging, first raised questions. "The integrity of this championship, which is the largest puzzle competition in the U.S., is our highest priority, and we will take every step to ensure that it is maintained," Devine said. "Championship officials expect to complete their investigation in the next few days."

Shortz, also the puzzle master for NPR's Weekend Edition and crossword editor of the New York Times, said by phone that he, Baxter, and Inquirer officials would examine Varshavsky's puzzle results "and all the puzzles in the competition, and we'll also be looking at video and photos from the competition."

"I've been directing the American Crossword Puzzle Championships for 32 years and have hosted The Inquirer championships for three years, and this is the first time I'm aware of even the possibility of any attempts to cheat at any of these events before," Shortz said. "It took me by surprise, I must say. It would be difficult to cheat in a competition like this, but I now see how it could be done."

Philadelphia will be the host of the World Sudoku Championship in April. Snyder, speaking by phone from Stanford, Calif., said the prestige of the city as host was at stake.

"If they did nothing," he said, "it would change my perspective, and that of any serious competitors, on traveling to Philadelphia and competing for significant prize money."

Snyder said his attention was drawn to Varshavsky when the latter "turned in his completed puzzles right after I did" in the second round, showing great speed and facility.

"The community of best solvers are very much friends and share solutions and strategies," Snyder said. "Here was this new guy in a hoodie, acting mysterious and very, very confusing. Yet then, when he had to solve a problem on stage, under intense scrutiny, I saw he was in no way able to solve it."

Even a difficult Sudoku puzzle may have relatively easy initial steps, Snyder explained. "Even a new player should have been able to fill in a few squares." Because of an error by Snyder, Varshavsky had a full 20 minutes to complete the puzzle and try for the second-place prize, but he failed to fill in more than one or two squares.

On his blog, "The Art of Puzzles," Snyder wrote that "competitors were [unfortunately] allowed to wear headphones to listen to music and could have electronic devices such as iPods as timers on their desks, the opportunity for something unknown to be hidden under this 'hoodie' such as a camera/transceiver that would allow a person outside of the room to use a computer solver to relay a solution back to a competitor, was great."

Contact staff writer John Timpane at 215-854-4406, jt@phillynews.com, or twitter.com/jtimpane.