James Toney has been stripped of his WBA heavyweight title victory after failing a post-fight drugs test.
The American won the crown by beating John Ruiz on points last month but was relieved of it by the New York State Athletic Commission on Wednesday.
The Commission confirmed that he had violating its illegal substance policy and also suspended him for 90 days.
Under WBA rules, the title could now revert back to Ruiz, who ended his brief retirement earlier this week.
NYSAC chairman Ron Scott Stevens told Reuters the Commission was requesting the Toney-Ruiz result be adjusted to a 'no decision'.
Stevens would not say what banned substance had been detected in Toney's drugs test.
"This is a medical issue and it would be a breach of his confidentiality and the privacy that we owe him," he said.
Toney's promoter, Dan Goossen, issued a statement on behalf of the boxer denying he had knowingly taken any performance-enhancing drug.
"Toney received medical treatment for recovery from his biceps and triceps surgery last year," the statement said.
"His doctor has stated that the combination of medications used to control the inflammation and tissue growth caused the positive test result."
Stevens said he believed it was the first time New York had ever changed a title fight result because of a drug violation.
He said the decision could be appealed within 30 days, which would set up an open hearing.
