Seven weeks after the World Health Organization declared Liberia to be free of the Ebola virus, the country’s deputy health minister said the body of a 17-year-old man had tested positive for the disease. The deputy minister, Tolbert Nyenswah, who also heads Liberia’s Ebola response, said Monday that the teenager had died Wednesday in Nedowein, a town close to Liberia’s international airport, and was given a safe burial the next day. He said the man was not tested until after he died. It was not known how he had contracted the disease. Mr. Nyenswah said the case was being investigated, but that people should not panic because there were no other known cases in Liberia. The W.H.O. declared Liberia to be Ebola-free on May 9 after the country went 42 days without reporting a case. The virus, which has killed more than 11,100 people in the current outbreak, has lingered in neighboring Guinea and Sierra Leone.