FORT WORTH (NYTIMES) - At least six people were killed in crashes that involved at least 100 vehicles on a Texas interstate Thursday morning (Feb 11), authorities said, as a slurry of winter weather made for slick roads, patches of ice and dangerous driving conditions.

Multiple people were also trapped in their vehicles by the crashes, which took place just after 6 am along Interstate 35 in Fort Worth and included cars and 18-wheeler trucks, according to the Fort Worth Fire Department.

Videos broadcast by local TV stations showed cars piled on top of one another, tractor-trailers rolled onto their sides and other vehicles spun out along the roadway as firefighters worked the scene.

Thirty-six people were taken to hospitals, including three who were in critical condition at the scene, said Matt Zavadsky, a spokesman for MedStar Mobile Healthcare, an emergency services agency working with the Fort Worth Police and Fire departments.

Sixty-five others sought medical care from area hospitals throughout the day, and the numbers were expected to increase, officials said. Among those injured were four officers, who were treated at area hospitals and released.

The Fire Department said in a statement that at least 100 vehicles were involved in the accident.

At a news conference, Officer Daniel Segura of the Fort Worth Police described the crash as "a massive accident pileup" said that the scene 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.

All northbound lanes of the interstate were closed because of "a major accident due to weather," the Police Department said, and the highway was backed up in both directions for long distances.

"Seek alternate route," the department urged travelers in a tweet.

The police set up a site for families to pick up and meet drivers and passengers who were involved in the pileup.

Neil Noakes, chief of the Fort Worth Police Department, said at a news conference Thursday afternoon that ice was a factor in the crash, which remained under investigation.