ALBUQUERQUE, N.M. — The case of a man who moved to the American West to search for $2 million in hidden treasure but turned up dead in New Mexico’s backcountry was officially closed after authorities struggled to solve the mystery.

Investigators recently informed Randy Bilyeu’s family, bringing some closure after more than a year of uncertainty and heartache that began when the 54-year-old father and grandfather vanished in January 2016.

He was looking for a bounty that an antiquities dealer said he stashed somewhere in the Rocky Mountains. It has inspired thousands to search in vain across remote corners of New Mexico, Yellowstone National Park and elsewhere.

Bilyeu’s family members in Florida said Tuesday that they are relieved yet saddened that they may never know what happened.

“But we haven’t given up,” said Linda Bilyeu, Randy’s ex-wife and mother of his daughters.

Authorities have returned his cellphone and laptop to the family, who plan to go through the remainder of his belongings next week while keeping watch for any new information.

Linda Bilyeu said the family is moving forward but also is working to keep his memory alive by telling his story and warning other would-be treasure hunters to proceed with caution because the risks can be grave. She spent months organizing volunteers who used everything from canoes to drones to search for Randy Bilyeu.

His skeletal remains were discovered last summer by a crew with the Army Corps of Engineers that had been working along the Rio Grande.

Autopsy results obtained by The Associated Press showed there was not enough evidence for investigators to determine what caused Bilyeu’s death. He had no broken bones or other skeletal injuries, leaving only room for speculation.

Medical investigators said it was possible that Bilyeu was caught in a remote location in the winter either because of the weather or an injury and succumbed to hypothermia or dehydration.

He was among those drawn to the hunt after antiquities dealer and author Forrest Fenn of Santa Fe, New Mexico, announced several years ago that he hid a small bronze chest containing nearly $2 million in gold, jewelry and artifacts in the Rockies. He dropped clues to its whereabouts in a cryptic poem in his memoir, “The Thrill of the Chase.”

Bilyeu had moved to Colorado to search for the cache. He spent a couple of weeks scouting the area in New Mexico — a desolate, rocky stretch of the river not far from the border of Bandelier National Monument. He had a GPS device and waders and brought along his little white dog, Leo.

His ex-wife filed a missing person’s report on Jan. 14, 2016. Bilyeu’s raft and dog were found the next day.

Inside his car were maps with markings that fellow treasure hunters and volunteers used to narrow their search for him. He also left food, suggesting he didn’t plan to be gone long.

During the months spent searching for Bilyeu, his family urged Fenn to call off the treasure hunt. Fenn refused, saying that would be unfair to those who have spent time and money looking for the 40-pound chest.