Twenty-nine vehicles are involved in an accident on Oklahoma City Boulevard, firefighters said.
The accident happened Monday morning between Pennsylvania Avenue and Agnew, when freezing temperatures and freezing drizzle helped make the roads slippery in the state.
Five people were taken to local hospitals and one in critical condition, said Oklahoma City fire brigade chief Benny Fulkerson.
Firefighters said the vehicles were stacked next to each other.
Some other people involved in the accident went to hospitals on their own to be checked, said Fulkerson.
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Related video: OHP spokesman gives updates on the wreckage on Oklahoma City Boulevard