The sign language interpreter for Nelson Mandela's memorial on Tuesday was has been dubbed "a fake," CNN reported.

Although the interpreter looked like he was hard at work, translating the spoken words into gestures at the international icon's services, an association for the deaf community in South Africa said his actions outraged deaf people.

The Deaf Federation of South Africa said the "interpreter" was not a recognized professional.

"The so-called 'interpreter' who interpreted at the official memorial service for late former president Nelson Mandela at FNB stadium has been dubbed the 'fake interpreter' and the deaf community is in outrage," Bruno Druchen, national director of DeafSA, said in a statement. "He is not known by the Deaf Community in South Africa nor by the South African Sign Language interpreters working in the field."

Druchens said the interpreter did not use facial expression, which in South African sign languages are an important part of communication and the signs he made with his hands were meaningless and self-invented.

"The signs the interpreter used are not used in South African Sign Language and it is a total mockery of the language," Druchens said.

DeafSA said the man also did not use the established, recognized signs for the names of Mandela, South African President Jacob Zuma and his predecessor, Thabo Mbeki.

"This proves that he is not involved in the deaf community and doesn't know South African Sign Language," the organization said. "To the best of our knowledge, he has not undergone any formal training in South African Sign Language or Interpreting offered by any recognized institution which offers these training courses."

Mystery over his identity and employment continues to grow. A spokesman for the ruling African National Congress told CNN that they did not hire the interpreter for the event.

"We have used him on some occasions but yesterday was not an ANC event so we cannot answer for yesterday," spokesman Jackson Mthembu said.

CNN said the African National Congress did not name the interpreter.

Collins Chabane, minister in the presidency said the South African government is investigating reports about the poor sign-language interpretation at the memorial

The service for the former South African President, who died last week at the age of 95, was held at the Johannesburg's FNB stadium and was broadcasted to millions of viewers around the world.