The ambulance that rushed Nelson Mandela to hospital two weeks ago broke down, but the mishap did not endanger the anti-apartheid hero who remains in a serious condition, the South African presidency said on Saturday.
The 94-year-old is receiving treatment for a recurrent lung infection as he begins his third week in hospital.
"Mandela remains in a serious but stable condition in hospital," said Mac Maharaj, President Jacob Zuma's spokesman.
He refused to comment on a report by the US news channel CBS that Mandela was "unresponsive" and "has not opened his eyes for days".
Referring to Mandela by his clan name, the spokesman told AFP that "authoritative reports about Madiba's medical condition will come from the presidency, based on the reports the presidency receives from the doctors".
Mandela, who became South Africa's first black president in 1994, was taken to hospital in the early hours of June 8.
The ambulance that took him to hospital from his Johannesburg home to a heart clinic in Pretoria 55 kilometres (30 miles) away, had engine trouble and broke down en route. Another had to be called, Maharaj said.
CBS claims Mandela was stranded for about 40 minutes while waiting for the replacement ambulance. Maharaj refused to say how long Mandela's ambulance remained by the roadside, during the southern hemisphere's winter.
Maharaj claimed doctors were "satisfied" that Mandela suffered no harm during the wait for, and transfer to, a replacement ambulance.
The "fully equipped ICU (intensive care unit) ambulance" had a "full complement including intensive care specialists and ICU nurses", he said.
Ambulances breakdowns are uncommon in South Africa, the continent's wealthiest country, where vehicle repairs and maintenance are generally conducted to high standards.
Maharaj said that as a precautionary measure, the replacement military ambulance was accompanied for the rest of the journey by a civilian ambulance.
Saturday's update on Mandela's health status was the first from the presidency in five days.
Last Sunday Zuma told a rally that Mandela was showing "sustained" improvement.
On Monday, Mandela's daughter Zenani Mandela-Dlamini, South Africa's ambassador to Argentina, told reporters gathered outside the Pretoria hospital that he was "doing very well".
Thabo Mbeki, who succeeded Mandela as president in 1999, on Thursday said that the Nobel Peace Prize laureate was improving and was not going to "die tomorrow".
There were also reports later in the week quoting a grandson speaking of his looming release from hospital.
Mandela, who is due to celebrate his 95th birthday on July 18, has been hospitalised four times since December, mostly for the pulmonary condition that has plagued him for years.
With the latest hospitalisation, many South Africans have come to terms with the much loved icon's mortality.
Amid accusations that the government has hidden uncomfortable facts about Mandela's treatment, the ANC, which Mandela led for so many years, said Zuma's office had been "consistent and reliable".
"The ANC has no doubt that the reports they provide are indeed sufficient to ensure that, while respecting the privacy of the former president and his family, we are all kept up-to-date and knowledgeable about his condition."
The party added it trusted that "we all continue to keep him and his family in our thoughts and prayers".
Former South African President Nelson Mandela is pictured in Sandton, north of Johannesburg, on June 17, 2010. The ambulance that rushed Mandela to hospital two weeks ago broke down and another had to be called, but the mishap did not endanger the anti-apartheid hero, the South African presidency has said.
Zindzi, daughter of former South-African president Nelson Mandela, leaves the Medi-Clinic Heart Hospital in Pretoria on June 18, 2013. The ambulance that rushed Mandela to hospital two weeks ago broke down, but the mishap did not endanger the anti-apartheid hero who remains in a serious condition, the South African presidency has said.