Via Avanova, as trustworthy a source as you'll find:

A Thai restaurant's spicy chilli sauce sparked fears of a chemical attack and led police to evacuate a busy London street.

Police closed off three roads and evacuated homes as a mysterious cloud of acrid smoke hovered over Soho for three hours.....

As the ambulance service sent in its Hazardous Area Response Team Unit, firefighters wearing specialist breathing apparatus entered the deserted streets to seek out the source.

They broke down the door of the Thai Cottage restaurant - to emerge later carrying a huge cooking pot containing about 9lb of smouldering dried chillies.

Link via Rational Review.

UPDATE: The BBC is reporting this as well, so it just might be true. Also in that BBC clip: the recipe, for the culinary terrorist in all of us.