President Cyril Ramaphosa of South Africa has vowed to jail officials caught up in an ongoing corruption inquiry following the arrest of five people, including a witness at a judicial inquiry into alleged influence peddling.

Ramaphosa’s remarks made at a mining investment conference in Cape Town on Wednesday followed after up to five Western envoys including the United States and the United Kingdom threatened to cut foreign direct investment if no action was taken against perpetrators of corruption.

A South African police spokesperson Wednesday said  that Angelo Agrizzi, a former executive of a private company who testified for more than a week on how he bribed politicians and bureaucrats to secure government contracts for his company, was one of five people arrested on charges of corruption and fraud in the awarding of government contracts.

The five are charged with misappropriating about 1.6 billion rand ($44.5 million).

“These arrests are a culmination of many years of investigations,” said Hangwani Mulaudzi, the spokesman for the Hawks police unit.

Agrizzi’s lawyer, Daniel Witz, did not instantly respond to phone calls from Reuters seeking comment.

The five suspects appeared in a Pretoria court and were each granted 20,000-rand bail. The case has been postponed to the March 27.

Warrants were issued for the arrest of two others. One is overseas and the other is in the coastal city of Port Elizabeth, Mulaudzi said.

The arrests are linked to contracts awarded by the correctional services department to services company Bosasa Operations, now know as African Global Operations.

The inquiry where Agrizzi testified are public hearings on claims that corporate interests that include the Gupta brothers — the heads one of the country’s biggest conglomerates — unduly influenced former President Jacob Zuma over political appointments and winning contracts.

Wrongdoing which Zuma and the Guptas denied.