Two people are in a critical condition after being exposed to an “unknown substance”.
Wiltshire Police were called on Sunday afternoon to help a man and a woman in Salisbury who were subsequently taken to the city’s district hospital.
A number of locations in the city centre have been cordoned off and the A&E department at the hospital was closed on Monday morning.
Public Health England (PHE) said there was no “wider risk”.
A major incident has been declared at Salisbury District Hospital but neither police or the hospital have commented further.
A spokesman said: “PHE understands that those exposed to the substances have been decontaminated, as is standard practice in situations like this.
“Scientists from PHE’s Centre for Radiation, Chemical and Environmental Hazards will continue to assist the response and review information as it becomes available.”
Dorset and Wiltshire Fire Service was called to the hospital’s A&E department on Monday to help with the decontamination.
Routine appointments are going ahead as scheduled unless patients have been contacted directly and staff have been told to come in as normal, the PHE spokesman added.
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