Forty-eight people have been taken to 10 hospitals after two Chicago transit trains collided head-on early Monday morning, according to Forest Park Mayor Anthony Calderone.
None of the injuries were considered serious, he added, according to the Chicago Tribune.
The accident happened just before 8am and officials are currently investigating the cause, Chicago Transit Authority (CTA) spokeswoman Lambrini Lukidis reportedly said.
Lukidis also appeared to dispute the total number of people inured during the collision, saying 33 individuals were taken to 9 area hospitals.
According to local NBC affiliate WMAQ-TV, sources within the CTA said they were investigating whether or not one of the trains involved in the accident was taken from the yard without authorization.
Calderone reportedly added that the site is being treated as a crime scene "until it's ruled otherwise."
Martinez Butler, a locomotive engineer for another train company, witnessed the accident.
"There was a train that was stopped at the station. Another train came through and looked like it blew the signal, because I heard beeping," she said, according to WMAQ-TV. "I'm a locomotive engineer. I know the systems, I know the sounds. When you hear those beepings it's warning you that there is an obstruction in front of you and you need to stop."
"Stop! Stop! Stop the train!" a 17-year-old Taylor Pettiford reportedly said she heard people yelling before the crash. "Slow down!"
After the collision, Pettiford said she "instantly started crying" and called her mother to pick her up from the scene.
This is a breaking news story. Updates will be added.
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