Updated at 10:45 p.m. ET: At least three people were killed Saturday in two crashes each involving 20 or more vehicles in winter conditions on interstates in northwestern Pennsylvania, authorities said.

The fatalities occurred in a crash involving more than 20 vehicles and tractor trailers on westbound Interstate 80 between Clintonville and Emlenton at about 3 p.m. ET, the Venango County Police Department told NBC News. There were at least six injuries. The Pittsburgh Post-Gazette had a lower death toll -- two -- and said whiteout conditions contributed to the accident.

NBC station WICU of Erie said that the crash involved 50 vehicles and that more than 100 people were injured, but it did not cite sources.

A public information officer at the Grove Medical Center in Slippery Rock told NBC News that another accident involving 40-50 vehicles occurred around noon on Interstate 79. She said about 20 people were treated at the hospital, but all but one were released. The Post-Gazette said the interstate was closed for about three hours after the crash in the southbound lanes in Mercer County.

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