Blood tests have shown no evidence that Tommy Haas was poisoned during Germany's Davis Cup semi-final defeat by Russia in Moscow in September.
Haas missed his reverse singles match with stomach pains
An inquiry was launched after team-mate Alexander Waske claimed someone had told him Haas, who had gastro-enteritis during the tie, had been poisoned.
But tests commissioned by the International Tennis Federation (ITF) did not support the claim.
Russia won both reverse singles matches on 23 September to beat Germany 3-2.
A statement said: "Following enquiries, the ITF has concluded that there is no medical information or other evidence whatsoever to support recent speculation concerning the medical condition of Tommy Haas during Germany's Davis Cup semifinal tie against Russia.
"There will be no further comment on this subject."
Speaking last week, Haas said: "It's no longer an issue. The tests gave no results. It was too far in the past."
Haas was beaten in straight sets on the opening day of the semi-final, which Russia won 3-2, and was unable to play in the reverse singles.
After reading Waske's comments, he underwent tests in New York "to be absolutely clear about what was happening to my body".
During the same visit, he also underwent minor surgery on his right shoulder.
The world number 12 will now take six weeks off from training but hopes to be fit enough to compete in the Australian Open, which starts on 14 January.