LAS VEGAS (AP) -- Veteran boxer Leavander Johnson underwent brain surgery and was in critical condition Saturday night after collapsing in his dressing room following his IBF lightweight title loss against challenger Jesus Chavez.

Johnson's promoter said doctors told him the fighter's brain swelled during surgery and they were inducing a coma to try and control it.

"He's not in good shape," Lou DiBella said.

Johnson left the ring on his own accord but began having trouble walking on his way back to the dressing room after being stopped by Jesus Chavez in the 11th round of their title fight at the MGM Grand hotel-casino. DiBella said he was revived but passed out again in the ambulance on the way to the hospital after complaining of a bad headache.

DiBella said he was told by doctors that Johnson suffered a subdural hematoma, which is bleeding in the brain area. He said he seemed aware and conscious going into surgery, but said later that doctors described his situation as grave.

Johnson was listed in critical condition in the hospital's intensive care unit after the surgery.

The 35-year-old fighter from Atlantic City, N.J., who was defending his 135-pound title against Chavez, took a tremendous beating throughout the fight.

The fight was part of a card promoted by Oscar De La Hoya that featured bouts with Marco Antonio Barrera and Shane Mosley.

The fight was stopped 38 seconds into the 11th round by referee Tony Weeks but not before Johnson took what appeared to be about two dozen unanswered punches to the head while he was up against the ropes.

Weeks declined to talk about how quickly he stopped the fight. Some ringside observers were yelling at the referee to stop the fight before the final few punches.

Nevada Athletic Commission member Tony Alamo, though, said the referee acted properly.

"The referee did a great job and we support his stoppage at the appropriate time," Alamo said.

After the 10th round, ringside physician Margaret Goodman checked on Johnson in his corner but allowed the fight to continue.

"Basically he was fine. He was alert," Goodman said. "I talked to him and there was no change in his neurological state. It was the same thing afterwards. I asked him if he had a headache and was dizzy. He said no."

Another doctor, William Berliner, accompanied Johnson back to his dressing room. Berliner said Johnson began dragging his leg on the way back to the dressing room and his handlers laid him down.

Berliner said Johnson never lost consciousness.

Chavez dominated the fight, landing big punches to Johnson's head from the opening bell. Statistics compiled by Compubox showed him landing 409 punches to 148 for Johnson.

After the fight at the MGM Grand hotel-casino, Johnson said in the ring that "I'm all right," but later collapsed in his dressing room.

Johnson was defending the title he won June 17 when he stopped Stefano Zoff in Italy. It was the first title for Johnson since he turned pro in 1989 after an amateur career that spanned 126 fights.

The injury follows the July 2 death of Mexican boxer Martin Sanchez, who died a day after he was knocked out by Rustam Nugaev of Russia in a super lightweight fight in Las Vegas. That death was the fifth in the ring since 1994 in the city.

Before Sanchez died, two other fighters suffered brain injuries but survived after fights this year in Las Vegas.

"It's a concern for all of us," Goodman said.

The World Boxing Council later said it would launch an investigation into the death, saying there were lingering questions about the care given to Sanchez immediately after the fight.

A picture from the bout. Johnson is the fighter on the right.