Three people have been rushed to hospital after a medical helicopter has crashed while reportedly on a training exercise on Thursday evening.

The crash happened in Hartford, Illinois, around 9pm local time. Photographs taken at the scene show the helicopter badly damaged and upside down under a tree. Witnesses say the rotor clipped a tree limb mid-air, while attempting to take off, before the chopper spiraled down and burst into flames, according to Fox2.

Emergency services rushed to the scene with multiple fire departments in attendance. People on the scene told First Alert 4 that four people were pulled out of the helicopter before it caught fire. A witness said three people were transported from the scene to area hospitals.

A Facebook post made by the Hartford Fire Department just a few hours before the crash said the department was hosting a training exercise involving a helicopter landing in an empty lot by North Delamr and Date Street.

The Facebook post read: Hello Hartford Residents. "The Hartford Fire Department will be hosting ARCH Medical this evening for training. They will be landing a Helicopter this evening in the empty lot across Date Street.Please do not be alarmed. This is for training purposes only. If you would like to see the Helicopter up close, please DO NOT approach the Helicopter without authorization from ARCH. Helicopters can be Very Dangerous and this is one of the reasons for training. Thank you for your cooperation."

A spokesperson for ARCH Medical Services has provided the following statement: "This evening, at approximately 9 p.m. Central Time, the ARCH 1 crew from Granite City, IL, was involved in an incident as they were departing from a local fire station. All three crew members on board have been transported to local hospitals for evaluation. We continue to support our teammates and are working with the authorities in support of the investigation."

The cause of the crash remains under investigation. The Hartford Fire Department has been contacted for comment.