That estimate may only be the tip of the iceberg, the group said, as people may not seek medical attention for food poisoning and cases go unrecorded.

CNN: Food poisoning: What you need to know

The George Mason group concludes that investment banks tip trading clients about the upcoming downgrades, giving them a chance to put on bearish trades and profit from the inevitable stock decline.

FORBES: Tipping The Shorts

South African police received a tip-off about the presence of the group last September and infiltrated it, he is quoted as saying.

BBC: South Africa charges DR Congo 'rebels for coup plot'