JOHANNESBURG — South Africa’s government was confronted Friday with a new and chilling allegation about the bogus sign language interpreter at Nelson Mandela’s memorial: He was reportedly accused of murder 10 years ago.Officials said they were investigating the revelation by the national eNCA TV news station. But they were unable, or unwilling, to explain why a man who says he is schizophrenic with violent tendencies was allowed to get within arm’s length of President Barack Obama and other world leaders.Investigators probing Thamsanqa Jantjie “will compile a comprehensive report,” said Phumla Williams, the top government spokeswoman. But she did not say how long the investigation would take and insisted details would not be released until it was completed.“We are not going to sweep it under the carpet,” Williams said. “We want to own up if there is a mistake, but we don’t want to be dishonest” to Jantjie.An Associated Press reporter found Jantjie at a makeshift bar owned by his cousin on the outskirts of Soweto Friday, near his concrete house close to shacks and an illegal dump where goats pick at grass between the trash. Asked about the murder allegation, Jantjie turned and walked away without saying anything.