PHOENIX (AP) - Former heavyweight champion Mike Tyson's 4-year-old daughter is on life support after she was found with her neck on a treadmill cable Monday, police said.

The girl's 7-year-old brother found her on a treadmill with her neck on a cable attached to the exercise machine at their Phoenix home, police Sgt. Andy Hill said, calling it a "tragic accident."

The boy told the girl's mother, who was in another room. She took the girl off the cable, called 911 and tried to revive her.

Responding officers and firefighters performed CPR on the girl as they rushed her to a nearby hospital, where she was in "extremely critical condition" and on life support, Hill said.

"Somehow she was playing on this treadmill, and there's a cord that hangs under the console - it's kind of a loop," Hill said. "Either she slipped or put her head in the loop, but it acted like a noose, and she was obviously unable to get herself off of it."

Hill said former Tyson had been in Las Vegas but flew to Phoenix immediately after learning of the accident.

Tyson could not immediately be reached for comment. Calls to three of his representatives were either not returned or not answered.

Brief footage from local TV station KTVK showed Tyson arriving at the hospital in a white button-up and black pants, and looking around with a frown before going inside.

Hill said everything in the investigation pointed to an accident. "There's nothing in the investigation that revealed anything suspicious," he said.

He added that responding to calls involving children is an officer's most difficult duty.

"Those are the things that stay with you in your career," he said. "We always hope for a miracle - not to have the worst happen to a child."

The central Phoenix home where the girl lives is in a quiet neighborhood. It's a modest, single-story light yellow house with a large fountain in the front yard.

Neighbors were surprised and saddened when they heard of the accident.

"It's terrible," said Abby St. Jermain, who grew up in the neighborhood and is house-sitting for her parents down the street. "The kids are so sweet. We always see them riding their bikes, playing. They've just been wonderful people."

Dinka Radic, who lives across the street, described Tyson's daughter as smart and sweet.

"The little girl, she says 'You got chocolate in your house?'" Radic said. "I say 'Yes,' and she says, 'OK, give me some.'"

When she gives the girl the chocolate, Radic said "she just kisses me on my knees. Kiss, kiss, kiss. Very nice."