Whiteout conditions have caused a pileup of as many as 30 cars and trucks on a major highway in Oregon, leaving some drivers stranded in their vehicles, police said.

Several people were injured, and first responders were searching every vehicle caught up in Thursday’s chaos on Oregon’s I-84, near Multnomah Falls, about 25 miles east of Portland, the Multnomah County Sheriff's Office said.

“There are reports of people stuck inside their vehicles. Responders are making their way through the scene and checking on cars,” Multnomah County Sheriff’s Office said in a social media post. “We advise everyone to stay in their vehicles for their safety unless there is a clear or immediate reason not to.”

Police earlier estimated that more than 100 cars were involved in the pileup, but after “a more thorough assessment,” they said it was closer to 20-30 vehicles. “Low visibility made it difficult to differentiate initially between vehicles that were involved and vehicles that were only stopped,” they said.

A winter storm descended on the Pacific Northwest Thursday as police warned road conditions were “getting worse by the hour.”

An SUV in the pileup caught fire. Everyone in the vehicle managed to get out, police said.

Freezing rain and snow contributed to the pileup, where officials extended a state of emergency through at least Friday and said eight emergency shelters would be open.

Officials said 489 people went to the shelters Wednesday night. Wind chill readings could dip to 10 degrees in Portland, the weather service said.

One couple driving toward Portland told KATU that they were caught up in the crashes.

“The visibility was so low by the time we got to the stopped traffic," a woman named Jade told the outlet. "We tried to stop; we ended up smashing into a semi-truck and another passenger truck and got stuck there for a minute. We heard somewhere crashes behind us, so we decided to go ahead and go through, in between the semi-truck and the median.”

The “incident on Interstate 84 was caused by multiple crashes congesting the area. We do not have a solid number as we are working through them all and the poor visibility makes estimating difficult, but it is dozens of vehicles,” said a spokesperson with Oregon State Police.

“Most of the reported crashes are non-injury or minor injury. There are no known fatal injuries or even serious injuries at this time. OSP and partner agencies are working to clean up the area; however, extended delays are to be expected,” the spokesperson added.