STEAMBOAT SPRINGS — The cause of death for missing Steamboat Springs resident Matthew Shelters remains a mystery.

“Everything we have so far is indicative of this just being an accident,” Routt County Sheriff Garrett Wiggins said Thursday. “We have no evidence at this point that gives us any thought of foul play.”

Shelters was reported missing April 27. He was last seen leaving Back Door Grill on Oak Street at about 12:20 a.m. April 24.

On July 4, his body was discovered badly decomposed next to Soda Creek on private land just outside city limits.

“It makes us wonder what in the world was anybody doing in this area,” Wiggins said.

The sheriff said it is believed Shelters might have been coming from a nearby trail downstream.

An autopsy was performed to try to determine a cause of death.

There were no signs of trauma, and a cause of death could not be determined.

Toxicology tests to determine if Shelters had any toxins in his system are still pending.

Forensic pathologist Dr. Michael Burson in Loveland has been tasked with determining the cause of death.

“The toxicology is taking a long time just because there was not much to work with, and they have to retest,” Routt County Coroner Rob Ryg said.

Wiggins said the toxicology tests are going to show the presence of toxins, but it won’t show the amounts. Toxicology tests typically determine amounts of toxins, but that information likely won’t be available because of the limited samples they were able to collect.

“It will say he had X, Y, Z in his system,” Wiggins said. “I think we pretty much concluded our investigation unless something comes up with the tox results. That unknown could put a different twist on the investigation.”

Wiggins said investigators have spent “countless hours” trying to determine what happened to Shelters.

“We’ve followed up on a lot of rumors,” Wiggins said. “We’ve followed up on a lot of speculation.”

DNA samples were also taken and sent to a lab, but Wiggins said they were told results would not be available for seven to eight months.

“We’re very certain that this is Matthew Shelters, but we just want to provide some finality to the family and us,” Wiggins said.

To reach Matt Stensland, call 970-871-4247, email mstensland@SteamboatToday.com or follow him on Twitter @SBTStensland.