At least 30 people were injured in a series of multiple car pile-ups that shut down parts of a Pennsylvania highway in the aftermath of a major storm in the North East.
The accidents are believed to have involved up to 100 vehicles during the rush hour.
Aerial images showed turned over cars, jack-knifed lorries and crashed vehicles on the icy highway.
Pennsylvania State Police believe drivers were driving too close and too fast for the conditions, and that may have contributed to the pile-ups.
A winter storm has dumped snow and ice on many states, leaving at least 21 people dead, cancelling thousands of flights and disrupting deliveries on Valentine’s Day.
Among the victim was a pregnant woman struck by a snow plough in New York. Her baby was later delivered and was in a critical condition.
As the storm moved from the South through the Northeast, the mix of snow and sleet grounded more than 6,500 flights nationwide and closed schools, businesses and government offices.
About 1.2 million utility customers have lost power.
The treacherous weather was blamed for nearly two dozen deaths, many of them in motor vehicle accidents. There was no immediate word on any casualties in the Pennsylvania accidents.
Boston, New York, Philadelphia and Washington were all badly affected.
In New York, residents braced for up to 14 inches (35cm) of snow before conditions started improving today.
It was a lot even for New Yorkers used to tricky weather.
Already late to the office, Brain Fesen said: “It’s taken a long time to get to work, to walk on the streets.
“People are ploughing, it’s just a rough day to get to the office.”
Mayor Bill de Blasio faced criticism for his decision to keep schools open on Thursday.
In the South, roads remained clogged and travel disrupted.
About 1,000 people spent the night on cots and mats at Charlotte airport in North Carolina.
Across the state in Durham, motorists stuck in traffic that resembled the gridlock mess in Atlanta two weeks ago found refuge for the night at a mall.
Around the country, this is shaping up as one of the snowiest winters on record.
As of early this month, Washington, Detroit, Boston, Chicago, New York and St Louis had received up to three times as much snow as normal at this point in the season.
The storms and cold blasts are blamed in part on a kink in the jet stream, the high-altitude air currents that dictate weather.
