Zuma and the Guptas - a family of wealthy Indian-born businessmen - deny any wrongdoing.
Besides the pressure from the ANC, Zuma is facing a no-confidence motion in parliament set for February 22.
Zuma's silence has fuelled speculation of a power struggle behind the scenes with deputy president Cyril Ramaphosa, whose election to the head of ANC in December marked the beginning of the end of Zuma's tenure.
SAFTU also continues to insist that these crimes are not confined to a few businesses, families and politicians - a "Guptocracy" - but is an inherent feature of a monopoly capitalist system, whose ruling class captured the state years ago and still dominates economic policy-making today.
"These guys are searching all the rooms‚ literally going through the place inch by inch".
A senior judicial source said police expected to arrest up to seven more people and that Gupta family members would be among them.More news: Oregonian snowboarder Ben Ferguson makes 12-man final
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"Finally something is being done about it. They have done enough damage", said Tessa Turvey, head of the local residents' association, standing outside the compound's iron gates.
A security guard told Reuters that police raided the Oakbay holding company's offices on Wednesday.
The ANC said on Tuesday it had made a decision to "recall" Zuma, a euphemism for removing him from office, but gave him no firm deadline to resign, setting the stage for a potential fight to wrest him from power.
Tense negotiations were still under way by Wednesday evening with the lawyers of five suspects arrested by the Hawks in connection with the R220 million looted from the failed diary farm in Vrede, Free State.
He declined to give details of what was seized or if the business premises of the Guptas would also be raided, saying a full statement would be released later on Wednesday.
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