"The Churchill County Sheriff’s Office along with the Lyon County Sheriff’s Office is investigating the death of Naomi Irion as a homicide," the Churchill County Sheriff's Office said in a Thursday afternoon Facebook post.
While "the exact cause of death is known," authorities are not releasing that information "at this time as the circumstances around that event if released would compromise the ongoing investigation," the sheriff's office said.
The 18-year-old was allegedly abducted from a Walmart parking lot, where she regularly parked her car to take an employee bus to her job at a Panasonic factory, around 5 a.m. on March 12.
Troy Driver, 41, has been arrested and charged with first-degree kidnapping in connection to the teenager's disappearance. Lyon County Judge Lori Matheus set his bail at $750,000 during a hearing on Wednesday. Driver was sentenced to 15 years in prison in 1997 for his role in covering up a murder and a string of robberies, according to local records obtained by News 4 and FOX 11 Reno.
"My sister's death is officially being investigated as a homicide," Irion's sister, Tamara Cartwright, wrote in a Thursday tweet.
The Churchill County Sheriff's Office said Irion's remains were recovered in the area of Coal Canyon Road within Churchill County.
"No further information can be released at this time as this is still an open and active investigation," authorities said in the Facebook post. "The Churchill County Sheriff’s Office and the Lyon County Sheriff’s Office will continue to work closely on these cases and as updates that do not compromise the investigation are available we will relay them."
Surveillance footage released by the Lyon County Sheriff's Office shows a suspect walking from a nearby homeless camp to the parking lot and getting into the driver's seat of Irion's car, then driving away in an "unknown direction with Naomi in the passenger seat."
It is unclear if the person on the surveillance footage is Driver.
Police located Irion's vehicle in Fernley, Nevada, on March 15, three days after she was last seen in the parking lot.
Irion grew up in several countries with her family as her dad works for the U.S. State Department in the foreign service. She moved from South Africa to Nevada last August and was living with her brother, Casey Valley, in Nevada.
Anyone with information about the circumstances leading to Irion's death can call their local FBI field office or the Lyon Sheriff's office at 775-463-6620.
Fox News' Paul Best contributed to this report.