Officials continued to search Friday for an aircraft carrier Nimitz sailor who has been missing since May 4, when he went hiking in a Washington state national forest and never returned.

Electrician’s Mate Nuclear Power 2nd Class Jeremiah Adams went out alone for a day hike in the Olympic National Forest, according to police.

His friends got worried when he didn’t show up for a hike last Saturday, and they called the sheriff’s office on Monday when he didn’t show up for work, according to Clallam County Sheriff’s Deputy Brian King.

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Adams’ car has been found at one of the trail heads, and search operations are ongoing for the 24-year-old, he said.

“We’ve come up with really zero, no tangible evidence that’s assisting us in further identifying a potential location where he may have gone,” King said. “We have his vehicle, we have a trailhead, it’s our assumption that is where he went.”

The trail is popular, so finding distinct footprints or other clues has proven difficult, he said.

The search has involved scent dogs using clothing in Adams’ car, as well as cadaver dogs, King said.

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Olympic National Forest and the adjacent park “is rugged country,” he said.

“Don’t hike alone,” King warned. “While the majority of hikers are safe every day, there’s a lot that can happen to a person when you’re hiking alone.”

Adams joined the Navy in 2013, shortly after graduating from high school in the Chicago area, his mother, Christine Adams, told the Chicago Tribune.

He took up hiking with all the opportunities in Washington state, and enjoys it because it let him get out in nature, particularly after months at sea, she said.