A third-place finish at a tournament last month by a formerly obscure player was so startling that organizers searched his clothing and took apart his pen looking for evidence that he had outside help. They found nothing.

But the episode has again raised the question of how officials can monitor games in an era when technology is so advanced, and it set off concerns about how such suspicions will affect the game. If every out-of-the-ordinary performance is questioned, bad feelings could permanently mar the way professional players approach chess.

The player most recently scrutinized was Borislav Ivanov, 25, a low-ranked master from Bulgaria, who won five games, drew two others and lost two at a tournament in Zadar, Croatia. The five victories were against four grandmasters and a strong master, and Ivanov soundly defeated them all.

One of Ivanov’s losses was in a long game in a closed position (the kind where computers perform poorly), and at the end, Ivanov made a rudimentary mistake. It stood out because of how well he had played in the other games. The other loss was in the penultimate round, when the organizers, as a precaution, stopped broadcasting the games on the Internet so that people outside the playing hall could not try to assist the players.