South Africa's government said it is preparing a statement. Jackson Mthembu, spokesman for the governing African National Congress party, declined to comment. "Government will be able to assist you," Mthembu said.
Druchen and two other sign language experts said the man was not signing in South African or American sign languages. South African sign language covers all of the country's 11 official languages, according to the federation.
Nicole Du Toit, an official sign language interpreter who also watched the broadcast, said in a telephone interview that the man on stage purporting to sign was an embarrassment.
"It was horrible, an absolute circus, really, really bad," she said. "Only he can understand those gestures."
South African parliament member Wilma Newhoudt-Druchen, a member of the ruling party who is deaf and who is married to Druchen, also said the man communicated nothing with his hand and arm movements. AP interviewed both Druchen, who also is deaf, and Newhoudt-Druchen by telephone using an interpreter.