CHICAGO -- Two teenagers have pleaded guilty in the sexual assault of a 15-year-old girl that was streamed live on Facebook in March.

In a plea deal with Cook County prosecutors, the 15-year-olds pleaded guilty to a single count of child pornography and will be sentenced to probation. Judge Patricia Mendoza said Tuesday she would decide the length of the probation by their January sentencing.

Both suspects were originally charged with aggravated sexual assault and manufacturing and dissemination of child pornography.

At the time of the assault, authorities said as many as six males assaulted the victim, a high school freshman who went missing after she was dropped at home by an uncle.

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Police said the assault was watched live by about 40 viewers, none of whom called authorities to report the attack.

Prosecutors said in April that the girl was threatened with a dog attack if she tried to flee.

During the initial hearing for one of the two boys charged in the case in April, Assistant State's Attorney Maha Gardner said the other suspect had told the victim she could "have sex the easy way or the hard way."

"Both videotaped these egregious actions," Gardner said. "They didn't stop there. They put them up on Facebook for the world to see."

Gardner said the 15-year-old, who turned himself in Monday, was with another boy when they encountered the 15-year-old girl in a neighborhood park on March 19 and lured her to a basement in the West Side neighborhood of Lawndale, where authorities say she was assaulted. Both boys knew the girl, the prosecutor said.

She was taken to the basement where she was sexually assaulted on a bed by both suspects as others watched and recorded video of it.

The prosecutor says the suspects also threatened to sic a pit bull on the victim if she tried to leave.