By Michele Corriston
Updated December 07, 2015 at 05:23 PM EST
Credit: Grant Lamos IV/Getty Images

This article originally appeared on

Kristin Cavallari is thanking her fans for their support as Utah police investigate her brother’s disappearance.

Michael Cavallari’s 2014 Honda Civic was found abandoned off a Utah highway on Nov. 27, the day after Thanksgiving, and authorities are treating the case as an open missing person investigation.

“I appreciate all the concern, thoughts, and prayers that have been extended to me and my family,” Kristin, 28, captioned an Instagram on Monday of her and Michael posing on a beach as children. “We remain hopeful and I will share any news that we receive. I have such gratitude for all those that have shared their support.”

“There’s no sign of foul play that we can tell,” Sheriff Steven White of the Grand County Sheriff’s Office told the Today show. “We’re still piecing everything together.”

Anyone with information regarding Michael should contact the Grand County Sheriff’s Office at 435-359-8115.