Klitschko is seeking answers regarding a sudden drop in odds just prior to the April 10 fight and the whereabouts of his postfight drug and urine specimens.
Klitschko has hired lawyer Judd Burstein and is seeking answers from Daniel Bogden, the U.S. District Attorney in Nevada. The letter of inquiry claims Bogden is looking into the possibility that Klitschko was drugged or poisoned prior to, or during, the bout.
"I have thought long and hard about requesting an investigation because I am concerned that the public, and particularly my fans, will see me as making excuses instead of taking responsibility for a loss," Klitschko said. "That is not my intention. I simply want to know the truth."
In his bout with Brewster at Mandalay Bay, Klitschko was knocked down at the end of the fifth round. As he stumbled to his feet, referee Robert Byrd stopped the fight.