(CNN) A massive crash sent 19 people to hospitals as thick fog and ice covered a Virginia highway Sunday.

The crash happened around 4:30 a.m. on the eastbound lanes of Interstate 64 near the Nelson-Augusta county lines, Virginia State Police spokeswoman Corinne Geller said.

"Heavy fog and icy road conditions are to blame," Geller said.

Plz continue to use caution while traveling over/near #Afton & #BlueRidge Mountains today. Fog & icy conditions were to blame in this AM's crash on I64 in #NelsonCounty involving a tractor-trailer & chartered bus. 19 injured. #SlowSpeed for conditions. #BuckleUp #ArriveAlive pic.twitter.com/0OEXKARTVm — VA State Police (@VSPPIO) November 17, 2019

The driver of a tractor-trailer lost control, and the semi truck filled with mail overturned, state police said.

A nearby charter bus wasn't able to avoid the overturned semi and struck it.

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