The crash on Interstate 275 near the Cincinnati suburb of Colerain Township was one of at least four pileups that snared dozens of vehicles. Officers were called to the scene shortly after 11:30 a.m. and discovered multiple chain-reaction collisions.
The 12-year-old girl had gotten out of a damaged vehicle and was standing in the median near a cable barrier, a type of fencing made of rope-like steel wire cables, the Hamilton County sheriff's office said. Another vehicle hit the barrier, snapping a cable, which then struck the girl and killed her, office spokesman Jim Knapp said.
At least 20 people were taken to hospitals, though their injuries were not expected to be life-threatening, the office said.
The interstate was shut down for hours with wreckage strewn across it, authorities said.
"It was just chaos, absolute chaos," Hamilton County sheriff's office Lt. Tory Smith told The Cincinnati Enquirer.
The sheriff's office said the crash remained under investigation, but it noted that inclement weather was a factor. Snow had been accumulating on the roadway, and there were reports of ice. Visibility was poor.
Parts of the state saw scattered snow showers on Monday, with isolated pockets of heavier snowfall.
As many as 50 vehicles were in a pileup on I-75, between Middletown and Monroe, in southwest Ohio. A dispatcher with the State Highway Patrol said minor injuries were reported in the accident, which occurred just before noon.
State Highway Patrol Sgt. James Russell told The Middleton Journal that snow falling at the time of the pileup caused "white-out conditions" and possibly triggered the first drivers to lose control and start the crash.
Witness Luke Stevens, of Van Wert, told the newspaper he was in a vehicle at the front of the pileup.
"It was complete ice all over the highway," he said.
Four semitrailers and about 20 cars were involved in an afternoon pileup on I-71 near Mansfield, the state patrol said. And lanes of I-270 were closed temporarily following a multi-vehicle crash near Columbus.