Authorities in Utah have launched a missing person investigation into the disappearance of Michael Cavallari, the brother of reality star Kristin Cavallari.

Cavallari, made famous by her role on MTV's reality series "Laguna Beach," is also the wife of Chicago Bears quarterback Jay Cutler.

Grand County Dispatch was contacted Nov. 27 regarding an abandoned vehicle off the side of the road, according to investigators. Authorities said they believe Michael Cavallari was the driver.

The vehicle, a 2014 Honda Civic, was registered to an individual in San Clemente, California, according to the Grand County Sheriff’s Office.

The sheriff's office said credit card transaction receipts led investigators to a convenience store in Monticello, Utah. Security footage from the store also showed Michael Cavallari as the driver of the vehicle.

I appreciate all the concern, thoughts, and prayers that have been extended to me and my family. We remain hopeful and I will share any news that we receive. I have such gratitude for all those that have shared their support. A photo posted by Kristin Cavallari (@kristincavallari) on Dec 7, 2015 at 7:33am PST

The Orange County Sheriff's office has also confirmed that Michael Cavallari was arrested on Nov. 23 on suspicion of making criminal threats. He was then bailed out of jail on Nov. 25.

Kristin Cavallari thanked fans for support and shared an apparent photo of her and her brother as kids on Instagram on Monday.

"I appreciate all the concern, thoughts, and prayers that have been extended to me and my family," she wrote. "We remain hopeful and I will share any news that we receive. I have such gratitude for all those that have shared their support."

Anyone with information on Michael Cavallari's whereabouts is asked to contact the Grand County Sheriff's Office at 435-259-8115 or www.grandcountysheriff.org.

