Two people were in critical condition, Elmwood Park Fire Chief Michael Marino said. No one aboard the train was reported injured.
Cars were strewn about the area and other drivers were helping rescue people trapped inside as emergency crews arrived around 5 p.m. Two people had to be extricated from their vehicles, including a woman whose car caught fire after she was out, Marino said.
CBS News reports
The rail crossing where the accident happened cuts through a busy diagonal intersection, and a street sign beside the tracks reads: "Long crossing. Do not stop on the tracks."
Wednesday evening, cars were backed up on the road, and the traffic was stop-and-go when the express train headed from Chicago to Antioch came through.
CBS station WBBM-TV in Chicago reports from the scene there is a mass of wreckage and metal that is difficult to tell was once cars.
Eye witness Van Jackson told WBBM that due to traffic, cars became sitting ducks on the train tracks. As the train approached, many jumped out of their cars and ran to avoid getting hit.
Metra spokeswoman Judy Pardonnet said it appeared that crossing gates were working properly when the train went through the intersection, though witnesses gave conflicting reports.
Christina Rodriguez, 29, of Chicago said her car and several others were trapped between the crossing gate arms when they came down.
"I saw the train lights," she said. "I tried to move but I couldn't move. Nobody moved." She said she jumped from her car seconds before the crash and ran to safety.
John Pease, 32, who lives near the site said he didn't see any warning lights flashing. "The gates were definitely up," he said.
Greg Sandford, 27, said he didn't see any flashing lights when he drove across the tracks. He was about five car lengths away when he saw the crash in his rear view mirror.
"The van in front of me stopped short and I stopped short, and 30 seconds later the Metra train just plowed through," Sandford said. "The train hit maybe six or eight cars, and they hit other cars and they careened into my car."
Two women were listed in serious condition at Loyola University Medical Center in Maywood, spokeswoman Anne Dillon said. Four others were Gottlieb Memorial Hospital in Melrose Park with injuries not considered life-threatening, said nursing supervisor Pete Eget.