Fog to the east and heavy snow to the west caused traffic chaos on both flanks of Denver on Friday.

In Aurora, a tour bus full of crew members for indie-rock musician Twin Shadow slammed into the back of a stopped semi-trailer on Interstate 70 in dense fog, injuring a dozen people, one of them seriously.

Meanwhile, in the mountains, westbound I-70 was closed from C-470 to Beaver Brook for most of the morning and into the afternoon as cars slipped and slid trying to make it up the incline. The Colorado State Patrol said snow tires and chains were required — even for cars — but added that even then they would recommend against driving in the mountains. Eastbound I-70 was also closed for part of the morning between Silverthorne and the Eisenhower Tunnel.

All of I-70 had reopened by 1:30 p.m.

Foggy conditions resulted in approximately 50 flights being diverted from Denver International Airport between 8 a.m. and 2 p.m., said airport spokesman Heath Montgomery.

PHOTOS: View more images from Friday’s crash on I-70

One plane, Republic Flight 4934 from Kansas City, Mo., operating as United Express, sat on the tarmac at Colorado Springs for more than six hours after being diverted before the flight was eventually canceled. Republic said the delay was caused by a lightning advisory and additional ground stops in Denver. The airline said passengers were offered a chance to leave the plane and would be offered compensation.

The Aurora crash set off a chain reaction that involved another tour bus carrying the crew of a second band — country western duo Thompson Square — and a second tractor-trailer.

“I’ve been in an accident. I’m in pain but I am conscious. Help is here,” Twin Shadow bass and keyboard player Spencer Zahn texted his mother, Dorrelle Zahn.

The Colorado State Patrol said the person seriously injured in the crash, 41-year-old John Crawford, was driving the Twin Shadow tour bus that initially sparked the wreck. Eleven others aboard that bus had minor to moderate injuries and were taken to Aurora hospitals.

University of Colorado Hospital received seven patients from the crash, according to Dan Weaver, a hospital spokesman. The Medical Center of Aurora said it received five passengers, all of whom have been treated and released.

The State Patrol said dense fog likely caused the 8:30 a.m. wreck in the westbound lanes. Heavy rain and snow were also falling at the time.

The patrol said alcohol and drugs do not appear to be factors.

“No charges have been filed but the case remains open,” officials said in a news release.

Twin Shadow is a Brooklyn, N.Y.-based artist who has concerts scheduled for the Bluebird Theater in Denver on Friday and Saturday night. The Friday night concert has been canceled. Thompson Square, made up of Keifer and Shawna Thompson, is still set to play Friday night at the National Western Complex Arena.

Twin Shadow left Lawrence, Kan., after a Thursday concert there.

“I told him I’d fly out there and he said no need,” Dorrelle Zahn said of her son, adding that when she tried to get more details about his injuries, he wouldn’t say.

Dorrelle Zahn said band members with Twin Shadow typically sleep in bunks between cities.

Chaney Bryant, operations manager for Las Vegas-based Gaines Motor Coaches, which owns one of the two tour buses involved in the accident, said he has been trying to learn details about the crash.

“We have great concerns. One of our coaches is down, and there have been injuries,” Bryant said.

Gaines caters mostly to musical touring groups. The coaches include front and back lounges, bunk beds, a kitchen and a bathroom with showers, Bryant said.