Mandela, 94, was hospitalized June 8 for a lung infection and has been in an intensive care unit since then.
Mac Maharaj, a spokesman for South African President Jacob Zuma confirmed Saturday an ambulance that brought Mandela to the hospital broke down, CBS News reported.
Maharaj said the ambulance was a "fully equipped military ICU ambulance" with a "full complement of specialist medical staff including intensive care specialists and ICU nurses."
"The convoy included two quick response vehicles," Maharaj said. "When the ambulance experienced engine problems it was decided that it would be best to transfer to another military ambulance which itself was accompanied for the rest of the journey by a civilian ambulance."
The spokesman said "all care was taken to ensure ... Mandela's medical condition was not compromised by the unforeseen incident. The doctors attending are satisfied that the former president suffered no harm during this period."
One of Mandela's grandsons, Ndaba Mandela, said his grandfather was getting better and may be discharged soon.
The former president, who was jailed for 27 years for his work fighting apartheid in South Africa, contracted tuberculosis in the 1980s while in prison. The disease is believed to have damaged Mandela's lungs, the BBC said.