At 10:30 a.m. Thursday, search crews located remains officials believe to belong to Michael. The body is being transported to the Utah Medical Examiner to determine the cause of death, according to the Grand County Sheriff's Office.
Kristin posted a touching tribute to her brother on Instagram.
"My heart is in a million pieces," she wrote. "Mikey, I could always count on you to make me laugh. You had such a good heart and will be forever missed. I'm at a loss for words but I know u are in a better place and finally at peace. I love u so much RIP"
Officials said Michael's body was discovered in the Salt Wash area near exit 175 on I-70 in Grand County, which is described as having steep and rocky terrain.
"We want to thank everyone for their love, support and prayers during this very difficult time. We have just been informed by the authorities my brother's body has been found," Kristin says in a statement to PEOPLE. "This is a very painful time and we are still processing it all. We kindly ask everyone please respect our privacy during our time of grieving."
Courtesy Grand County, Utah, Sheriff's Office
Kristin's former The Hills costar and friend Audrina Patridge tells PEOPLE: "That is such terrible news. My prayers go out to Kristin and her family."
On Monday, Kristin, 28, uploaded an Instagram photo of herself and her brother as kids, writing, "We remain hopeful … I have such gratitude for all those that have shared their support."
"Her brother was always a troubled kid and there was always drama with him," the source told PEOPLE.
Orange County Sheriff's Department records indicate that Michael was arrested on Nov. 23, just days before his disappearance, and briefly held in an Orange County Jail.
The source added that, despite his troubled past, he and Kristin had always been close.
"She was always very protective of him," the source said. "She was always trying to help him. He had been trying to produce reality shows awhile ago, but it didn't work out."
with reporting by AILI NAHAS