The U.S. State Department and Interpol are reportedly working with authorities in Slovenia to investigate the disappearance of a 25-year-old American man there. Jonathan Reid Luskin, a Wisconsin resident who had recently been working as a teacher in Hong Kong, was last seen on June 22, when he departed a family vacation in Vienna and ventured off for Ljubljana, Slovenia, by train. His mother, Susan Stone, told ABC News he hasn’t been heard from since telling a friend later that day he planned to go hiking in Slovenia's Triglav National Park. “He had an account with Citibank in Hong Kong and there have been no withdrawals since the middle of June,” Stone said. Slovenian police have confirmed that they are investigating Luskin’s disappearance with help from Interpol and police in Croatia, Austria, Greece, the U.S., and China.