British police declared a major incident late on Tuesday after it said a man and a woman in a critical condition may have been exposed to an unknown substance near the southern English town of Salisbury.
“Wiltshire Police and partners have this evening declared a major incident after it is suspected that two people might have been exposed to an unknown substance in Amesbury,” the police said in a statement.
WATCH: British counterterrorism police investigating after unknown substance leaves 2 people critically ill
“Emergency services were called to an address in Muggleton Road, Amesbury on Saturday evening (June 30) after a man and woman, both in their 40s, were found unconscious in a property,” the police said.
Amesbury lies 11 kilometres to the north of Salisbury, where in March Russian former spy Sergei Skripal and his daughter Yulia, fell severely ill after being poisoned by nerve agent.
Police on Wednesday said it was initially thought the man and woman in Amesbury had possibly used crack cocaine or heroin from a batch of contaminated drugs, but it added that further testing was ongoing.
WATCH: Chemical weapons watchdog backs U.K. on Novichok attack on Sergei Skripal, daughter
A Public Health England (PHE) spokesman said: “The current advice from PHE England, based upon the number of casualties affected, is that it is not believed that there is a significant health risk to the wider public. This will be continually assessed as further information becomes known.”
The man and woman were being treated at Salisbury District Hospital, which remains open as usual, police said.
© 2018 Reuters