A U.S. student who was missing for more than a week in Siberia has been found dead, Russian officials said. Colin Madsen allegedly left the guesthouse where he was staying at around 5 a.m. last Sunday wearing only a T-shirt and pants, despite the freezing temperatures. Russian investigators said Madsen’s body was found about a mile from the village where he was staying on a hiking trip with friends. Officials said there were no signs that the Missouri native had been injured or robbed, and his cause of death hasn’t been determined. A statement from the agency suggested the 25-year-old’s death may have been related to drugs, and police are testing his body for narcotics, ABC News reported. A murder investigation into Madsen’s disappearance will remain open until the circumstances of his death are known, officials said.