The warning follows the arrest of a police constable on fraud charges relating to the misuse of a state petrol card.
"I will leave no stone unturned in ensuring that corrupt members are brought to book and dealt with harshly in accordance with the law," said Molatjana.
Molatjana also urged anyone with information about police officers who are involved in corruption or fraudulent activities to contact their nearest police station or the National Anti-Corruption Hotline on 0800 701 701.
"We will treat their information with confidentiality. They must not be afraid to inform us about these corrupt officials," she said.
Constable Cassias Shai, 31, stationed at Leboeng police station, was arrested on July 17 together with petrol attendant Shadrack Masuku, 39, of Kgautswane village near Leboeng outside Ohrigstad.
"It is alleged that Shai conspired with Masuku, who is the petrol attendant, to swipe the official petrol card and pour petrol amounting to R584.43 into a private car," provincial police spokesman Lieutenant Colonel Mohale Ramatseba said.
They were not asked to plead to charges of fraud and corruption when appearing in the Lydenburg Magistrate's Court on 19 July.
They were released on a warning and the case was postponed to 13 September for further investigation.
