From The Guardian:
Major incident declared after man and woman found unconscious in Amesbury
A government source did not play down the potential severity of the incident, saying it was a matter of concern and was being closely monitored
A number of sites in the Amesbury and Salisbury area were cordoned off as a precaution, although the force said it was not yet clear whether the pair were the victims of a crime. Tests were being carried out to establish the substance that led to them becoming ill
Neighbours said they believed the two people who fell ill had been at a hog roast organised by Amesbury Baptist church. They were said not to be regular churchgoers. The Baptist church was cordoned off
www.theguardian.com/uk-news/2018/jul/04/wiltshire-unknown-substance-leaves-pair-critically-ill-in-salisbury-hospital