"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.
Four government departments involved in organizing the historic memorial service distanced themselves from the hiring of Jantjie, telling the AP they had no contact with him.
A fifth government agency, the Department of Public Works, declined comment and referred all inquiries about Jantjie to Williams' office.
Williams said the investigation would include trying to determine who hired Jantjie or the company he said he worked for. She did not say how long the probe might take, and police spokesman Lt. Gen. Solomon Mogale said there would be no additional information released until after Mandela's funeral Sunday in his hometown of Qunu.
The government is also trying to determine how Jantjie received security clearance and what vetting of his background — if any — took place. Officials at the State Security Agency, in charge of security for the event, have not commented publicly and by Friday had not responded to questions submitted by email a day earlier by the AP.
The government says the owners of the interpreting company have disappeared, and the AP was unable to track down the school where Jantjie said he studied signing for a year. An online search for the school, which Jantjie said was called Komani and located in Eastern Cape Province, turned up nothing.
Ingrid Parkin, principal of the St. Vincent School for the Deaf in Johannesburg, said she and other advocates for the deaf had never heard of the school. She added that there are no known sign language institutes in the province.
The Star newspaper of Johannesburg reported Friday that Jantjie said he studied sign language interpretation in Britain at the "University of Tecturers."