President Barack Obama looks down as he stands next to the sign language interpreter as he makes his speech at the memorial service for former South African president Nelson Mandela at the FNB Stadium in Soweto near Johannesburg, Tuesday, Dec. 10, 2013. South Africa's deaf federation said on Wednesday that the interpreter on stage for Mandela memorial was a 'fake', (AP Photo/Matt Dunham) JOHANNESBURG (AP) - The South African government said Friday it is aware of reports that the bogus sign language interpreter at Nelson Mandela's memorial once faced a murder charge, and said he is being investigated. Phumla Williams of the government communications office said the government is investigating Thamsanqa Jantjie and how he was selected to interpret at a memorial Tuesday at which he stood close to U.S. President Barack Obama and other leaders. "We will come back and give a full report," Williams said of questions surrounding Jantjie. She said she and other officials are currently focusing on mourning events, which have included three days of public viewing of Mandela's casket and will end with the anti-apartheid leader's burial on Sunday. Jantjie outraged deaf people by making signs they said amounted to gibberish. A South African TV news outlet, eNCA, reported that Jantjie faced a murder charge a decade ago, but it is unclear if the case was concluded. He also reportedly faced other criminal charges. Asked by an Associated Press reporter about a murder charge, Jantjie turned and walked away without commenting. U.S. Assistant Secretary of State for African Affairs Linda Thomas-Greenfield said "we're all very upset" about the bogus interpreter, who appeared just three feet from Obama at the memorial ceremony for Mandela, who died in his Johannesburg home on Dec. 5. Thomas-Greenfield told reporters in Kenya on Friday that U.S. officials are concerned about security and how the interpreter could have gotten so close to a number of world leaders. South Africa's arts and culture minister, Paul Mashatile, apologized for the use of Jantjie and said reforms must be implemented to ensure such an incident won't happen again. Without passing judgment, nobody should be allowed to undermine our languages. We sincerely apologize to the deaf community and to all South Africans for any offense that may have been suffered," Mashatile said in a statement." He did not comment on who was responsible for hiring the sign interpreter for Tuesday's memorial. Several government departments involved in preparations for Tuesday's memorial have denied hiring Jantjie. The African National Congress, South Africa's ruling party, said the state was responsible for all arrangements. Jantjie told AP on Thursday he has been violent in the past and hallucinated during the memorial service as he was gesturing incoherently. Thomas-Greenfield also said officials are dismayed because the people who need sign language weren't able to understand what was said at the ceremony. She called the problem "extraordinarily sad." In Washington, Secret Service spokesman Ed Donovan said Thursday that vetting for criminal history and other appropriate background checks of the people onstage were the responsibility of the South Africans. He added that Secret Service agents are "always in close proximity to the president." AP reporter Jason Straziuso in Nairobi, Kenya contributed to this report.