NEW YORK, June 6 (Reuters) - An American student who disappeared while on a family vacation in Japan was found dead outside Kyoto, his mother wrote in a Facebook post on Saturday.

o The body of James Higginbotham, 20, was discovered in a mountainous area by a volunteer search-and-rescue group, Nancy Higginbotham wrote.

o A cause of death and further details were not immediately available.

o "Our family is heartbroken," she wrote. "The grief we feel is impossible to put into words."

o Higginbotham, an Alabama resident and an engineering student at Auburn University, was last seen leaving a Kyoto train station on May 29. Later that night, his phone went dark and its location services were turned off, his mother previously told Reuters.

o Until then, she was able to track his movements using the app Life360, she said.

o His parents believe he was heading to a nearby hiking trail. Nancy Higginbotham had told Reuters she believed her son may have "needed space."

o The Higginbotham family was visiting Japan to celebrate the high school graduation of James Higginbotham's younger brother.

o An initial search by Japanese authorities lasted three days and included around 100 police officers, K-9 units and helicopters, but did not uncover any trace of him, CNN reported.

(Reporting by Milana Vinn in New York; Editing by Sergio Non, Rod Nickel)

By Milana Vinn