In pictures: 130-vehicle pile up on icy Texas highway leaves six dead

A massive crash involving more than 130 vehicles on an icy Texas interstate left six people dead and dozens injured amid a winter storm that dropped freezing rain, sleet and snow on parts of the US.

At the scene of the crash on Interstate 35 near downtown Fort Worth, a tangle of semitrailers, cars and trucks had smashed into each other and had turned every which way, with some vehicles on top of others.

"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," said Fort Worth Fire Chief Jim Davis.

At least 65 people were treated at hospitals, with 36 of them taken by ambulance from the crash site, including three with critical injuries, said Matt Zavadsky, spokesman for MedStar, which provides the ambulance service for the area. Numerous others were treated at the scene and released, he said.

The Fire Department said that more than 100 vehicles were involved in the accident. At a news conference, Officer Daniel Segura of the Fort Worth Police said the scene of the "massive accident pileup" extended about 1 mile.

A spokesman for the Fire Department said that crews had to use tow trucks to disentangle the cars and that they went vehicle by vehicle to make sure that drivers and passengers had been extricated from the wrecks.

The crash happened about 6 a.m., as many hospital and emergency workers were heading to and from work, so some of those involved were health care workers and emergency responders, including police officers, officials said.

"The roadway was so treacherous from the ice that several of the first responders were falling on the scene," Zavadsky said.

Zavadsky said his crews carry a sand and salt mixture in the ambulances, which they used at the scene. At one point, he said, one of the ambulances was hit, but it sustained only minor damage and the crew members were fine.

The ice storm came as a polar vortex - swirling air that normally sits over the Earth's poles - has moved near the US-Canada border, resulting in colder weather farther south than usual, said Steve Goss, a meteorologist with the National Weather Service's Storm Prediction Center in Norman, Oklahoma.

"As a result we're getting unusually or unseasonably cold air that's spilling south across a good portion of the United States east of the Rocky Mountains," he said.

In Tennessee, police responded to about 30 traffic collisions and some flights were delayed at Memphis International Airport after freezing rain and sleet fell.

In Kentucky, the governor declared a state of emergency to free up funding and help agencies coordinate as they responded to reports of slick roads and downed power lines. And in southern Indiana, schools and government offices closed.

In suburban Austin, more than two dozen vehicles were involved in a pileup on an icy highway, and five people were taken to a hospital, emergency officials said.