The International Tennis Federation are investigating claims from Germany's Alexander Waske that his Davis Cup team-mate Tommy Haas was poisoned during the semi-final defeat to Russia.
Doubles specialist Waske told German tabloid Bild: ‘I spoke with a Russian from Moscow at the Davis Cup. He said completely casually that Haas had been poisoned.’
Haas played on the opening day of the tie on September 21 but lost in straight sets to Igor Andreev.
The Germans turned the contest around and went into the final day 2-1 ahead.
Haas, however, was unable to take to the court on the Sunday for his reverse singles clash with Mikhail Youzhny due to stomach pains - and his replacement Philipp Petzschner went down in four sets.
Russia then clinched the decider with Andreev beating Philipp Kohlschreiber.
An ITF spokesman has confirmed the organisation is investigating the matter and Haas is expected to undergo a full medical in the United States on Thursday.
