South Africa’s competition matters adjudicator, the Competition Tribunal, on Thursday said it had inflicted a R534 million ($50 million) fine on Sasol Chemical Industries (SCI), a unit of the Johannesburg and New York listed petrochemicals giant, Sasol.

The penalty came after SCI was found guilty of overcharging its South African clients after collecting exorbitant amounts for purified propylene and polypropylene.

SCI was fined R205.2 million ($19.1 million) in the case of purified propylene and R328.8 million ($30.6 million) in the case of polypropylene, the Tribunal said.

The Tribunal also imposed the method the company would use for pricing of the two products in future. This will lead to a drop in the price that local competitors would have to pay for the two products.

The Tribunal said SCI’s transgressions happened during a period of four years, stretching from January 2004 to December 2007.

The Tribunal found that the prices SCI charged during the period had a negative impact on South Africa’s other plastic converters and SCI’s competitors.

Additionally, this hurt the firm’s competitors during the period covered by the Tribunal’s investigation.

The Tribunal’s finding follows a protracted inquiry into claims of excessive pricing by the SCI.

The inquiry lasted over several months from 13 May 2013 with the final submissions being made on May 9 this year.