(CNN) — Former world chess champion Vladimir Kramnik is being investigated for bullying and harassment following the death of fellow player Daniel Naroditsky , world chess governing body FIDE has announced .

Naroditsky, an American chess grandmaster who amassed a large online following through streaming and teaching, died unexpectedly at the age of 29, according to a statement released by his family via the Charlotte Chess Center on Monday. No cause of death was announced.

Kramnik, a grandmaster and the world chess champion between 2000 and 2007, had repeatedly accused Naroditsky of cheating in online games.

Naroditsky denied the accusations and, during his final Twitch stream last week, spoke about the mental toll Kramnik’s campaign had taken on him.

“The problem is, ever since

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