The news that Madiba -- the clan name by which the 92-year-old Nobel Peace Prize winner and country's first elected black leader is affectionately known -- was to spend a second night in hospital has gripped the nation.
The public has grown increasingly concerned for Mandela's health but he could be released as early as today, a source close to Mandela said on condition of anonymity.
"The old man is very sick but his condition is not life threatening," the source said.
"He came in for a checkup but the doctor decided to keep him in for observation.
"He is still not well but we expect him to be released tomorrow."
President Jacob Zuma
described the hospital visit as a checkup and called for calm, but a report said Mandela had been treated for a lung problem.
Mandela spent 27 years in prison for his role in the fight against apartheid in South Africa, emerging in 1990 to lead the transition to democracy.
