Klitschko was expected to beat the unknown Brewster

Judd Burstein sent the US Attorney's office a letter asking for an inquiry into the fight, in which Klitschko was beaten by American Lamon Brewster.

The letter claims the blood and urine samples taken from the Ukrainian boxer after the fight were missing.

Burnstein has also pointed out that the odds on Klitschko dropped dramatically before the heavyweight fight.

Klitschko was winning the fight on 10 April before Brewster knocked him out in the fifth round. He later said he felt drugged after the opening round.

Nevada Athletic Commission executive director Marc Ratner said nothing abnormal happened before, during or after the fight.

There were too many coincidences for me not to have suspicions Wladimir Klitschko's brother Vitali

"We were so concerned that night that we sent him to the trauma unit instead of the emergency room with a neurosurgeon in the ambulance," Ratner said.

"He took all the appropriate tests, both urine and blood. There was nothing in those tests irregular or remarkable."

Klitschko's brother Vitali, the new WBC heavyweight champion, claimed that Wladimir, who was as much as a 11-1 favourite against Brewster, was registered as 3-1 favourite just few hours before the fight.

"There were too many coincidences for me not to have suspicions," said Vitali Klitschko.