OKLAHOMA CITY (AP) - Oklahoma highway officials have re-opened Interstate 40 in downtown Oklahoma City after a 21-vehicle pileup at its intersection with Interstate 35.

The two cross-country interstates meet near downtown Oklahoma City. Freezing rain in advance of a snowstorm slickened the highway overnight Tuesday, and a semi-trailer jackknifed on a bridge over the Oklahoma River.

The pileup involved 10 crashes involving 21 vehicles, including three tractor-trailers. Several people were sent to hospitals.

Highway crews are warning drivers of "black ice," when the road appears wet but is actually covered by a thin layer of ice.

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