Rioters ran amok looting and setting structures ablaze in July after former president Jacob Zuma was sentenced to 15 months in jail for snubbing a corruption inquiry.

An agrochemical warehouse near the eastern port city of Durban storing chemicals used for making herbicides, pesticides and fungicides was one of the buildings torched.

Environment Minister Barbara Creecy said Sunday the "environmental impact of the chemical spill and fire incident... has caused the most serious environmental catastrophe in recent times".

Presenting the results of an investigation into the incident she said it "may take several years to recover from this incident".

Following the incident the local municipality closed beaches as a precautionary measure, and warned the public to refrain from fishing, surfing or picking up dead sea life. The beaches remain shut.

A criminal case has been opened against the company, UPL, who had no environmental permits to run their operations in the area, said the minister.

President Cyril Ramaphosa described the violence -- which claimed 354 lives and was the worst seen since the end of apartheid -- as an attempted insurrection.