A man in his 40s has been missing since Monday, when he was last seen at the head of a mountain trail on Kuchinoerabu, a volcanic island 12 km off Yakushima Island in Kagoshima Prefecture, Yakushima police said.
The man was identified as American Craig Arnold in an e-mail received by The Japan Times Thursday from Chris Arnold, who said his brother had been missing for 72 hours since heading to the island.
Police declined to confirm the missing man's identity.
According to police, the man was first reported missing early Tuesday after local residents, concerned he had not returned from his trip, searched the mountains to no avail. They reported the incident to the island's resident officer, who informed Yakushima police.
Yakushima police have dispatched 10 policemen, 20 firefighters, two police dogs and a helicopter to Kuchinoerabu to conduct daily searches of the area.
No trace of the man has been found so far.
Police said they were considering increasing the number of searchers.
Police said the volcanic, mountainous isle has numerous cliffs, which could potentially be dangerous for hikers.
Kuchinoerabu has a population of 150 and is a popular tourist destination with numerous hot springs and fishing spots.