CHICAGO (CBS) — Several expressway ramps were closed after a medical helicopter crashed along I-57 Saturday night.

Four people were sent to nearby hospitals.

CBS 2’s Vi Nguyen has the story.

Authorities said the crash happened after 9:00 Saturday night. The pilot called mayday and had to make an emergency landing.

The pilot was on board with two crew members and a patient. Emergency responders got to the scene and said the helicopter landed on its belly. The pilot was able to turn everything off and everyone on board was taken to the hospital.

Two crew members and the pilot are in stable condition. The patient is in critical condition.

Witnesses said they saw the helicopter in the air before the crash.

“I looked up at the sky and all of a sudden you could see a helicopter on fire, going out of control, trying to stabilize itself,” said witness Andres Herrera. “When it was in the sky it was already on fire.”

“I just saw the helicopter on fire, trying to get control, but he couldn’t,” said witness Breanne Coober.

A statement from Superior Ambulance reads in part “a company team of experts has been assembled and will be dispatched to the accident site to participate in an investigation, along with federal aviation authorities and the manufacturer of the helicopter.”

“The National Transportation Safety Board is the only authorized communicator in regards to the accident and all further information will come from the NTSB.”