The search for more bodies of miners killed in a shooting incident three days ago at Aurora's Grootvlei mine in Ekurhuleni was called off on Thursday because of darkness, Gauteng police said.

The search would resume on Friday morning at 9am, said Colonel Noxolo Kweza.

"We can confirm that four bodies were recovered from underground at the mine and we are still trying to retrieve more, but we cannot say how many are still under," Kweza said.

Allegedly killed by guards

They were allegedly shot dead on Monday by mine security guards who left them underground and did not notify the police.

Police could not say whether there had been a shootout and said this would be determined when post mortems were conducted.

The Aurora Mine, situated between Springs and Benoni, is co-owned by President Jacob Zuma's nephew Khulubuse Zuma and Nelson Mandela's grandson Zondwa Mandela.

The Sowetan newspaper reported on Thursday that mine security guards allegedly shot dead 20 people at the mine.

It was not clear whether those killed were illegal miners or unpaid Aurora employees.

Wage deadlock forces illegal mining - NUM

Expressing shock at the shooting, the National Union of Mineworkers (NUM) linked it to the mine's failure to pay its workers, leaving them "to fend for themselves".

"NUM calls for an urgent investigation into these allegations and whether or not these were indeed illegal miners," spokesman Lesiba Seshoka said in a statement.

Mine officials were not immediately available to comment.

'Guards kidnapped, one killed'

However, the website miningmx.com reported that Aurora Empowerment Systems had confirmed that illegal miners were killed at Grootvlei.

On the website, Grootvlei mine commercial director Thulani Ngubane reportedly denied that 20 people were killed.

He told the website mine management had been alerted to "a situation" after a kidnapped guard managed to escape.

"Last week one of our security guards was shot dead and another kidnapped by these illegal miners," he said.

'These people... kill our security'

"I am asking you, were these people within their rights to kill our security and steal from our mine?" Ngubane said to Eyewitness News.

The company has to date reported over 35 cases of illegal mining to the police.

Ngubane dismissed as untrue reports of a rampage by workers, explaining that Grootvlei had been shut down since April following a wage-related strike.

The Congress of SA Trade Unions (Cosatu) has backed the NUM's call for an urgent independent investigation into the allegations and into whether the miners were illegal.

It said anyone found guilty of unprovoked shooting should be charged, tried and punished.

Widespread condemnation

"Cosatu does not condone illegal mining, but even if the people killed were involved in illegal mining, that in no way justifies the brutal response allegedly meted out by the security guards," it said.

"They have the same constitutional right as every other citizen to a fair trial and appropriate sentence."

The ANC described the killings as "senseless".

"The mine management and the responsible security company should have sought the assistance of the South African Police on suspicion of crime being committed in their mine, rather than shooting at first instance," spokesman Jackson Mthembu said in a statement.

"We appeal to our law enforcement agencies to investigate this matter with the urgency it deserves."

Department of mineral resources spokesman Jeremy Michaels said the shooting was a criminal matter and needed to be investigated by law enforcement agencies.