A rescue effort was underway Monday morning for more than a dozen hikers who disappeared in California near where a wildfire was burning in the Tahoe National Forest.

According to a late Sunday night post on X from the Placer County Sheriff’s Office, 13 people ranging in age from 16 to 20 in "a large group" got lost hiking near where the Royal Fire was burning.

The forest, just northwest of Lake Tahoe, is located in portions of six counties: Sierra, Placer, Nevada, Yuba, Plumas and El Dorado.

On Monday morning, the sheriff's office posted an update a helicopter had located a group of hikers believed to the missing hikers.

"Search and rescue crews will be inserted to hike out with them," the department posted.

How big is the Royal Fire?

As of just before midnight Sunday, the United States Department of Agriculture Forest Service reported the fire spanned at least 54 acres.

"Law enforcement is evacuating recreation areas near the incident," USFS-Tahoe National Forest posted on X.

The cause of the fire remained under investigation on Monday, park officials said.

This is a developing story.

Natalie Neysa Alund is a senior reporter for USA TODAY. Reach her at [email protected] and follow her on X @nataliealund.