The embattled Gupta family was on Wednesday morning hoping to strike a deal with the Hawks after the special unit carried out a raid on the controversial family's Saxonwold compound in Johannesburg earlier in the day.
His resignation came just hours after police raided the luxury home of the Gupta family, Indian-born billionaire allies of the president who have been at the center of corruption allegations against Zuma and his circle for years.
Committee Chairperson Francois Beukman says this breakthrough shows a concerted effort by the Hawks to fulfill its mandate of investigating the misuse of state funds.
Hawks spokesman Hangwani Mulaudzi said the raid was part of a probe into influence-peddling allegations.
Zuma and the Guptas have always denied wrongdoing. Mr Magashule was elected secretary-general of the ruling African National Congress (ANC) in December.
The South African police on Wednesday raided the house of an influential business family suspected of using its ties to President Jacob Zuma to influence Cabinet appointments and land state contracts.
A Gupta family lawyer told Reuters none of the Gupta brothers were among those held.
Early this morning, as the plush suburb of Saxonwold was waking up - gardeners walking dogs, children being taken to school in 4x4s - armed police arrived at the enormous, high-walled, Gupta compound opposite the lion enclosure of Johannesburg Zoo, sealing off a section of the road, and venturing inside.
Signs of law enforcement mobilizing against the Guptas, and by association Zuma, caused the rand to strengthen 0.5 per cent against the dollar.
The ANC could throw its weight behind such a vote if Zuma, who has survived several no-confidence motions in the past, refused to heed its orders to resign.
They are known friends of President Zuma - and his son, daughter and one of the president's wives worked for the family's firms.
Besides the pressure from the ANC, Zuma is facing a no-confidence motion in parliament brought by the opposition Economic Freedom Fighters.