SAN BERNARDINO, Calif. -- Prosecutors declined Friday to file rape charges against former heavyweight boxing champ Mike Tyson, saying the case could not be proved.

The San Bernardino County district attorney's office reviewed the case and conducted a follow-up investigation before reaching a decision.

"It's precisely because of Mr. Tyson's reputation for violence and his notoriety and his previous conviction for rape that we really, really looked at this case very careful," said Deputy District Attorney David Whitney.

"We concluded after reviewing everything we currently know about the case that it cannot be proven beyond reasonable doubt."

Whitney said it was unlikely charges could be filed in the future.

A 50-year-old woman maintains she was sexually assaulted by Tyson on July 16 at a home he rented while training in this resort in the San Bernardino Mountains east of Los Angeles.

Tyson, who said he was innocent, left Big Bear for Phoenix to train for a Sept. 8 fight with Danish boxer Brian Nielsen in Copenhagen.

"There was never a doubt in my mind that, when the authorities took a hard look at the case, the truth would serve to vindicate me," Tyson said in a written statement. "Now that this is behind me, I am just looking forward to fighting and regaining the heavyweight championship of the world."

The woman's attorney, Gloria Allred, said she had no immediate comment on the case. She said she planned to hold a press conference Monday.

Although investigators were not able to interview Tyson, who declined through his attorney, they did interview three members of Tyson's entourage.

The 35-year-old Tyson served more than three years in an Indiana prison after being convicted in 1992 of rape and other charges.