Kristin Cavallari’s older brother, Michael Cavallari, has been reported missing after the car he was driving was found abandoned on a highway in Grand County, Utah.

Us Weekly reports that Michael has not been seen nor heard from since Friday, Nov. 27, the day after Thanksgiving.

According to the Grand County Sheriff’s Office, Michael’s 2014 Honda Civic was found five miles south of Interstate 70 and exit 175. A search for the driver ensued to no avail.

In a press release, the sheriff’s office said it is treating the case as an actie missing persons investigation.

The car was reportedly registered to a person living in San Clemente, California. Investigators are looking at credit card transaction receipts and surveillance from a convenience store in Monticello, Utah, to confirm that Michael was the driver of the abandoned vehicle.

Brother of former reality star Kristin Cavallari reported missing https://t.co/SWifNQXhFm pic.twitter.com/MUmGaix2IT

— ABC7 Eyewitness News (@ABC7) December 6, 2015

Neither Kristin nor her husband, Jay Cutler, have commented on the disappearance, according to People magazine.

Kristin Cavallari's brother, Michael, has been reported missing in a rural part of Utah. https://t.co/STTNOS7WHB pic.twitter.com/PK9amEEre4

— EntertainmentTonight (@etnow) December 7, 2015

On Sunday, Nov. 29, Kristin, 28, posted a pic of her newborn daughter, Saylor James, who was born on Nov. 23, saying she would be missing her 10-year high school reunion to care for her baby girl.

Really sad about missing my 10 year high school reunion last night…so many people I wanted to see…but at least I have a good excuse

A photo posted by Kristin Cavallari (@kristincavallari) on Nov 29, 2015 at 9:52am PST

Those with information on Kristin Cavallari‘s brother, Michael Cavallari’s whereabouts are asked to contact the Grand County Sheriff’s office at 435-359-8115.