Paramedics responded to the accident about 2:40 a.m. on the outbound lanes of the Eisenhower Expressway, according to officials. At least one person appeared to be ejected from their car.
Outbound lanes have been reopened after being closed for hours, Illinois State Police said.
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A child and adult were taken to Stroger Hospital in serious to critical condition, officials said. Their conditions were stabilized.
Three other adults were taken to Mount Sinai Hospital in serious to critical condition, officials said. Two of the three were stabilized.
One person remained in critical condition, authorities said.