According to American news network CBS a "new source" alleges that former president Nelson Mandela was "unresponsive for days" at the Pretoria hospital where he is receiving treatment and that his liver and kidneys are down to 50%.

CBS also claims that Mandela's ambulance broke down two weeks ago on the way to hospital – stranding him for 40 minutes.

It was also reported that Mandela's immediate family is discussing withdrawing treatment, questioning how much more medical scrutiny the aged man is expected to endure.

Mandela is 94 years old, he was admitted to Pretoria Medi-Clinic Heart Hospital for a recurring lung infection on June 8.

These allegations contradict reports by family and officials that Mandela's health is improving.

In an interview last week, President Jacob Zuma said Mandela was responding better to treatment: "We are very happy with the progress that he is now making following a difficult last few days."

Mandela's grandson Daba Mandela thanked people around the world for sending well-wishes to Madiba who, he said, was expected to be discharged soon.

Ndaba said his family was grateful for Madiba's life and they were not ready to contemplate his death, the Star reported on Friday.

"Only God can take him… but for us, as family, as long as he can still hear and understand what is said to him, and talk to us, we'll continue to celebrate him."

Ambulance 'broke down'
According to CBS News Mandela went into cardiac arrest the night he was taken to Pretoria Hospital and had to be resuscitated. While he was driven to the hospital the ambulance suffered an engine failure and was forced to wait for over 40 minutes for a replacement.

When the second ambulance arrived Mandela had to be transferred – in winter temperatures – to a second vehicle which could have had an impact on his condition, according to a cardiologist interviewed by CBS. 

The general expectation was that Mandela could be discharged from hospital to return home during the course of the week – although that sentiment is based on very little fact.

The presidency and Mandela family continued to provide very little detail on the elderly statesman's health, to the point of not formally confirming which hospital he is in.

Mandela's daughter Zenani on Monday said he is "doing very well", and a statement from his wife Graça Machel expressed gratitude for an outpouring of well-wishes during his hospital stay.

On Monday, individuals and small groups continued to add to the cards, placards, balloons and small bunches of flowers that have created a wall of well-wishes outside the service entrance to the hospital.

Some passers-by used the wall as a backdrop for photographs of themselves, much as various television crews did for live updates. Security remained tight, with police searching vehicles entering the facility.