An acclaimed US poet has gone missing during a visit to a volcano in Japan.
Craig Arnold, 41, vanished after hiking up to the volcano on the island of Kuchinoerabu-jima in the northern Ryukyu Islands of southern Japan.
Japanese authorities have launched a search mission for Mr Arnold, who is an assistant professor of English at the University of Wyoming.
He was in Japan on an exchange fellowship to work on a book about volcanoes around the world.
His brother Chris Arnold, who lives in New York, said Mr Arnold had set off for the volcano shortly after arriving at the island by ferry on Monday and checking in at a local inn.
When he hadn't returned by the evening, the inn staff went to look for him. They reported him missing at 2100 local time, and a formal search began that night.
The next day, police and fire crews, dogs and a helicopter joined the search.
Police said they had found Mr Arnold's tracks on a trail up to the volcano, but they didn't see any tracks coming down.
Chris Arnold said it was possible that after emerging at the top, his brother may have had difficulty finding the trail to get back down.
"I know my brother is tough and can survive in these conditions for many days, but I sincerely hope more manpower can be devoted to the search soon," he told the university's website.
Chris Arnold's wife, Augusta Palmer, said dense vegetation on the slopes of the volcano made helicopter searches virtually useless.
"They are really having to do it by lines of people walking across areas to make sure they're covered," she said.
Japanese law only requires authorities to look for missing people for three days, but University of Wyoming officials said the search had been extended until Sunday.
University President Tom Buchanan said: "The thoughts of the UW community are with Craig and his family.
"We hope the Japanese search team will be able to continue its work until he is found."
Mr Arnold's poetry has been anthologised in several volumes of the Best American Poetry series.