What's going on in the world of pro tennis?
Last week, former world No. 1 Martina Hingis said she tested positive for cocaine at Wimbledon this summer, though she says she never took drugs.
This week, German player Tommy Haas revealed in an interview with mass circulation tabloid Bild Zeitung that he believes he was poisoned during a match in the Davis Cup semifinal in Russia in September.
Haas is currently ranked No. 13 in the world.
"I never felt so miserable in my whole life as I did on the Saturday and Sunday nights in Moscow. Of the eight hours I should have been sleeping, I've spent six of them on the toilet," he is quoted as saying by German sports agency SID.
On the weekend of Sept. 21, Haas was beaten in straight sets by Russian Igor Andreev, the 33rd-ranked player, and Russia claimed a 3-2 win over Germany.
Allegations of foul play surfaced when German teammate Alexander Waske told Haas that an unnamed Russian sports agent suggested to him that Haas was poisoned ahead of the last match.
Oliver Quante, spokesman for the German Tennis Federation in Hamburg, Germany, told ABCNEWS.com, "Tommy told our president that he never felt so bad in his life and that he spent more time in the bathroom than in his bed. The team doctor saw him three times during the night before the game and gave him some shots."
Quante, who says his organization was surprised by media reports about possible poisoning, explains that the team had dinner together and Haas began feeling sick afterward.
"Our team doctor has assured us that based on his medical expertise there is no concrete reason to suspect poisoning, and that there is no need for further specific medical checks with regards to possible poisoning," Quante said.
However, the International Tennis Federation in London is now looking into the matter.
A spokesperson at the tennis federation told ABC News, "We've only just found out about those allegations. We're taking this serious, and we're looking into the case. But we will only start an investigation after we receive a formal complaint from the German Tennis Federation."
Haas, who is on a photo shoot in Rio De Janeiro, Brazil, has arranged to undergo individual tests Friday in New York. "I want to find out if any poison can be traced," Haas said, according to German sports agency SID.
When contacted by ABC News, Russian Tennis Federation spokesperson Almira Vorobei dismissed the whole matter as nonsense.
"The federation does not organize their food — it has nothing to do with that. They eat where they want. It is not the federation's responsibility."