Mandela's ambulance broke down, stranding him for 40 minutes

Updated at 7:35 a.m. ET June 22, 2013

(CBS News) PRETORIA, South Africa - One of Nelson Mandela's grandsons said Friday he expects Mandela to be discharged from the hospital soon. And the man who succeeded Mandela as president, Thabo Mbeki, said in a radio interview that Mandela's health is improving.

Watch: Choir sings outside Mandela's hospital

Mandela, 94, has been in the hospital for two weeks, fighting a lung infection.

However, what CBS News is hearing is completely at odds with statements from Mbeki. Sources tell us that Mandela's liver and kidneys are functioning at 50 percent, and he had a procedure to repair a bleeding ulcer and another one to insert a tube.

We're told he hasn't opened his eyes in days and is unresponsive. We also understand that Mandela family members are discussing just how much medical intervention is enough for an old and very sick man.

On Saturday, a spokesman for South African President Jacob Zuma released a statement saying that Mandela's condition remains serious but stable.

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CBS News has also uncovered more about what happened the night Mandela was taken to the hospital. We now know that Mandela went into cardiac arrest that night and had to be resuscitated.

Watch: Critics worry family, government are prolonging Mandela's suffering, below.

He was taken in the middle of the night in a military ambulance to Pretoria, but the vehicle broke down, and a seriously ill Mandela had to wait on the side of the highway for over 40 minutes for another one. We don't know why it took so long for a second ambulance to arrive, but he was eventually transferred to a second vehicle in freezing winter temperatures.

The South African government has confirmed there was engine failure, but it says great care was taken to ensure that Mandela's health was not compromised and that his doctors were satisfied the former president suffered no harm.

The statement that Zuma's spokesman released Saturday said that it was decided that transferring Mandela to the second military ambulance was the best course of action.

"The fully equipped military ICU ambulance transporting former president Nelson Mandela on 8 June 2013 had a full complement of specialist medical staff including intensive care specialists and ICU nurses," said the spokesman, Mac Maharaj. "The convoy included two quick response vehicles. 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.

"All care was taken to ensure that former president 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."

However, cardiologists we spoke to said any delay - especially for a man that old - is cause for serious concern and, while it is difficult to assess, could have had an impact on Mandela's condition.