A massive highway pileup in northwestern Indiana on Thursday killed three people and injured more than 20 people, police said.

Indiana State Police said the pileup on Interstate 94 involved about 15 semitrailers and about 15 passenger vehicles and pickup trucks.

They said one injured person remained trapped in a vehicle Thursday evening, hours after the pileup occurred.

The accident happened near Michigan City, which is about a 60-mile drive from Chicago.

Police said Michigan City provided two buses that were being used to warm people and transport the injured to hospitals.

Photos of the scene showed at least a dozen semitrailers jammed together the width of the highway near an overpass. Some passenger cars were sandwiched in the wreckage.

Coroners from surrounding counties were called to the scene.

Franciscan St. Anthony Health in Michigan City had received at least 10 patients, said Dr. Jim Callaghan, president of the hospital.

Callaghan said two of those patients had died and one was in critical condition. He didn’t have information about their injuries.

LaPorte County Coroner John Sullivan estimated an additional 15 to 20 people with less serious injuries had been taken to a LaPorte, Ind., hospital.

Indiana State Police said eastbound I-94 was expected to be closed through the night. Cranes and wreckers were being brought in to help clear the scene.

Dixie Juchcinski said the accident occurred during a snowstorm.

“When we first came to a stop, it was a complete whiteout,” Juchcinski said. “It was kind of a surprise to us because we could only see one or two cars in front of us.”

Another witness, Laura Burcham, said she was “in tears just looking at it.”

National Weather Service meteorologist Evan Bentley said heavy snow was reported in the area at the time of the crash. He said a band of lake effect snow moved in late in the afternoon, dropping 1 to 2 inches of snow an hour and reducing visibility to a quarter mile or less, with some reports of visibility near zero.