Fears held for motorists trapped in massive pile-up near Michigan City, Indiana

THREE people are confirmed dead and many more injured after being trapped under wreckage due to a multi-vehicle crash in Michigan City, Indiana.

"Too many vehicles to count" were involved in the crash, along with about 15 semi-trailers in one of the worst multi-vehicle crashes ever seen in the state

Fears were held for motorists who have been trapped for hours in the blistering cold, but Indiana State Police now say only one victim remains on the site as firefighters figure out how to rescue them from the caage.

"At this point, anybody being taken out alive is probably nothing short of a miracle," said LaPorte County Coroner John Sullivan said.

Roads were shut off but the traffic caused by the crash extended for miles.

"We removed vehicles and accessed some people that have been previously trapped. We're addressing those as we come to those, we have no idea how many others may still be located somewhere in the wreckage," said Lt. Peter Wood, Indiana State Police. "Right now the challenges are the cold and the darkness."

Earlier LaPorte County Coroner John Sullivan said the scene was "looking grim. There may be many more fatalities. The clock is working against us."

The traffic caused by the crash extends for miles. Source: Supplied

Vehicles were crushed under the mammoth power of the semi-trailers. Picture: WLS Source: Facebook

It is unclear how the accident begun, but witnesses claim heavy snow conditions were most likely to blame, with a "whiteout" - where visibility and contrast are severely reduced by snow - happening at about 2.30pm US time when the collision occurred.

"I was in tears just looking at it," witness Laura Burcham told ABC News. "I believe it was snowing at the time of the accident."

The race against the clock to search for survivors has brought inteational coroners and heavy equipment to assist people who may be stuck inside the cars that are trapped undeeath the semi-trailers.

"They're getting to them as quick as they can, with cranes, wreckers, extrication. There's multiple fire departments out there, doing the best they can," Coroner Sullivan said. "There's just so much destruction, they have to tear apart those vehicles and semis and move them little by little to see if there is a car undeeath them, or under a trailer."

A temporary morgue has been opened to deal with the fatalities.

It is reported at least 15 people were rushed to IU-La Porte Hospital with injuries, while those in a critical condition were sent to Franciscan St. Anthony's in Michigan City.

Heavy snow is not helping the rescue effort. Source: Supplied

It is believed some might need to be airlifted to hospitals with trauma centres.

"We've received three patients in critical condition and four others not in critical condition. We expect others of course, and have called in additional staff," said James Callaghan, Franciscan St. Anthony Health Michigan City.

Ruptured tanks from the crash has spilt fluorescent green diesel fuel across the scene, making for a dangerous and slippery rescue mission.