At least six people have been killed in a huge pileup involving more than 100 vehicles on an icy motorway in Texas.
At least 65 people have been taken to hospital, where three are in a critical condition. Other victims were being treated at the scene.
Many people remain trapped in their vehicles as firefighters work to rescue them.
Among the victims were doctors, nurses and other healthcare workers driving to and from their shifts.
Thursday's crash happened amid a winter storm that has brought freezing rain, sleet and snow to the southern US state.
Pictures from the scene on Interstate 35 near downtown Fort Worth showed jackknifed lorries and crushed cars and vans.
"There were multiple people that were trapped within the confines of their vehicles and requiring the use of hydraulic rescue equipment to successfully extricate them,” Fort Worth Fire Chief Jim Davis said.
One video showed a firefighter rescuing a dog from one of the vehicles.
The crash happened about 6am as many hospital and emergency workers were heading to and from work.
“We did see a large number of people that were victims of this accident that were in scrubs, that had hospital IDs on … in some cases, our folks would know those folks,” Zavadsky said.
Fort Worth police Chief Neil Noakes said three officers were en route to work when they were injured in the crash, and one officer was injured while working the scene.
He said all have been released from the hospital and that none of them suffered serious injuries.
“The roadway was so treacherous from the ice that several of the first responders were falling on the scene,” Zavadsky said.
The ice storm came as a polar vortex — swirling air that normally sits over the Earth’s poles — neared the US-Canada border, resulting in colder weather further south than usual.