CHEYENNE, Wyo. (May 4, 2009)--A week has passed since a well-regarded poet with ties to Central Texas disappeared on a Japanese island and his sister-in-law says the search will go on for at least one more day.

University of Wyoming professor Craig Arnold, 41, vanished April 27 while hiking up a volcano on a tiny island in the northern Ryukyu Islands.

Arnold has been traveling all over the world, working on a book about volcanoes.

His sister-in-law, Augusta Palmer of New York, said Monday that Japanese authorities have committed to look for Arnold through at least Tuesday.

The search involves 20 to 30 people as well as search dogs and helicopters.

Japanese authorities say they've ruled out the possibility Arnold is either inside the volcano caldera or at the barren top of the volcano.

Last week, police reported finding Arnold's tracks on a trail up the volcano, but they couldn't find any tracks coming down, and the thick terrain is making helicopter searches virtually useless.

Arnold has published two award-winning collections of poetry: "Shells" in 1999, and "Made Flesh," which came out last year.

Arnold’s mother Judy said she last talked with her son on April 26 via the Internet teleconferencing site Skype.

Judy and John Arnold are longtime Temple residents and she used to teach Spanish at the University of Mary Hardin-Baylor.