Mchunu has rejected the allegations, describing them as “insinuations made without evidence or due processes”.
The 67-year-old politician had been suggested by local media as a potential candidate from the centrist faction of the ANC to succeed Ramaphosa.
Widespread corruption alleged
KwaZulu-Natal Provincial Commissioner Lieutenant-General Nhlanhla Mkhwanazi alleged on July 6 that Mchunu had received payments from a corruption suspect.
He also accused him of having played a role in dismantling a team investigating killings to shield politically connected people.
The commissioner, speaking at a media briefing flanked by armed security forces, some with their faces masked, said he had opened a criminal investigation into the minister.
He also accused other officials of obstructing police work against organised crime.
Mkhwanazi himself is under investigation for allegations of corruption in the awarding of a bulletproof-vest contract, the weekly Sunday Times reported.
Law professor and member of the ruling African National Congress (ANC), Firoz Cachalia, has been appointed as interim police minister.
South Africa ranks 82nd in the world according to the corruption perception index of the NGO Transparency International.
-Agence France-Presse