A Blue Line train bound for O'Hare International Airport derailed shortly after 5 p.m. Tuesday and sparked a fire, prompting the evacuation of scores of people through a smoke-filled tunnel, officials said.
The last car of an eight-car northbound train derailed, and material beneath the train caught fire, said Frank Kruesi, president of the Chicago Transit Authority.
A Fire Department spokesman said that at least 150 passengers were taken to hospitals, primarily for treatment of smoke inhalation. Most were in good or fair condition, officials said, but one hospital reported that two elderly patients were in serious condition.
Chicago Police Supt. Phil Cline said there was no evidence that suspicious activity was involved in the incident. "There is no indication of foul play at this time," he said.
According to Kruesi, the train, which originated in Forest Park, had just departed the Clark/Lake station when the motorman received a signal in his cab indicating there was a problem. He stopped the train and noticed smoke.
"He immediately called for the removal of power and evacuated the train," Kruesi said, noting the motorman had pulled to an emergency exit where passengers could climb to the street.
The rail line was shut down in both directions while investigators searched for the cause of the derailment and fire. The incident damaged the system's third rail and signals, but Kruesi did not know to what extent.
Passengers on the train said there was a sharp jolt before the train screeched to a halt.
"We were on the last car, and all of a sudden it started screeching and sparking," said Maryann Miceli, who was riding the train home. "It was all sparking and flames," she said. "That's when everyone started to panic."
Joel Johnson, 24, said he was on the train three cars from the back when "it felt like it jumped the line," and a fire started in the car behind his.
"People started running to the front. The whole place was filled with smoke," he said. "I could barely breathe."
Brenda Lopez, who was on the same car, said the train "dipped a little."
"I'm still kind of scared right now," she said. "You never expect it to happen on the train you're on."
The Associated Press contributed to this report.