"The woman, aged 44, and the man, aged 45, who are both local to the Wiltshire area and are British nationals, are currently receiving treatment for suspected exposure to an unknown substance at Salisbury District Hospital. They remain in a critical condition. It was initially believed that the two patients fell ill after possibly using drugs from a contaminated batch. However, further testing is now ongoing to establish the substance which led to these patients becoming ill," Mills said in a statement.
At this stage, it is not yet clear if a crime has been committed, Mills noted.
No one else was receiving treatment, except for the two victims of the alleged poisoning, the deputy chief constable pointed out.
Earlier in the day, the police said there had been a major incident in the area involving the possible exposure of two people to an unknown substance after a man and woman were found unconscious on Saturday.