CHICAGO, July 7 (Xinhua) -- At least four people were rushed to hospital Saturday night after an air ambulance helicopter crashed along Interstate 57 in Chicago suburb, Chicago Fire Department officials said.
Of the four injured, one was in critical condition and the other three were in serious condition, said a tweet from the Chicago Fire Department.
The incident occurred at about 9:15 p.m. local time (1415 GMT) when the medical helicopter carrying a patient was on its way to the city's far south side, police said.
Witnesses saw the helicopter spiraling out of control and on fire before it crashed, reports said. The pilot had issued a mayday call before the crash.
Federal Aviation Administration officials have identified the helicopter as a Eurocopter 135 air ambulance, and are investigating the cause of the crash.
