They rounded up and arrested hundreds, and engaged in running battles with angry mobs in Johannesburg, parts of the East Rand and Pretoria. By the time the violence subsided, 10 people were dead.

But a confidential briefing document News24 has seen, shows the many warnings available to the government and law enforcement authorities that attacks were being planned, and that something deadly was brewing. This, combined with other news sources, shows how xenophobic threats spread on social media in the lead-up to the attacks.

The police told News24 that they believed the attacks, which began on September 1, were triggered by a spontaneous fire, that could not have been prevented with intelligence, and that the incidents were mainly criminal in nature, and not necessarily xenophobic. 

But the document and publicly available evidence raises critical questions about how much the country's law enforcement and intelligence agencies knew about the wave of attacks, and why they seemed unable to prevent it.

The briefing document also shows that the government believes more violence could be coming.

The document sets out the background to the attacks, the key influence of social media, an assessment of the current situation, a prognosis and also mitigating measures.

It concludes that the key drivers of anti-migrant sentiment are that migrants are involved in crime, allegations of the illegal occupation of RDP houses, the employment of migrants instead of locals, the dominance of migrant-owned "tuckshops" in informal settlements and the influence of social media.

News24