PRETORIA, South Africa — A man accused of masquerading as a sign-language interpreter during Nelson Mandela’s memorial service, after he stood beside President Obama and other global dignitaries and gesticulated in gibberish, told interviewers on Thursday that he was a violence-prone schizophrenic and had seen angels descending in the stadium where the event was held.

The assertions by the man, Thamsanqa Jantjie, 34, whom sign language experts have called an impostor, added one more bizarre turn to a story that has raised questions about the security at the memorial ceremony and spread a pall of distraction and embarrassment over one of South Africa’s most solemn moments.

With Mr. Mandela lying in state here for a second day as thousands waited in line to pay their final respects, the government found itself unable to explain Mr. Jantjie’s selection for the job, admitted it had paid a bargain rate for his services and asserted that the company that supplied him had “vanished into thin air.”

Hendrietta Bogopane-Zulu, the deputy minister for women, children and people with disabilities, told reporters that Mr. Jantjie’s first language was Xhosa, among the most widespread among South Africa’s 11 official tongues.