The Collier County Sheriff's Office says someone from Texas called early Friday to report that a girl on a webcam in Naples was threatening suicide.
The girl said she was 17 and was holding a knife to her throat and arms.
An investigator was able to find the Web site and send the girl an instant message.
Posing as a young girl, the investigator got the girl to reveal the area where she lived. Deputies were able to find the house where she lived with her grandparents.
She was taken to a mental health center.
The incident comes about two weeks after a 19-year-old in Pembroke Pines committed suicide by taking a drug overdose in front of a live Internet audience.