EMERGENCY service bosses have praised staff and thanked the public for their responses in handling the major incident in Salisbury this week.

Chiefs from Wiltshire Police, Dorset and Wiltshire Fire and Rescue Service, Public Health England, South Western Ambulance Service and Salisbury District Hospital addressed reporters at a press conference this afternoon. 

But the panel would not be drawn on why it has taken seven days for information to come to light that hundreds of members of the public could have come into contact with a nerve agent.

Public Health England announced earlier today that up to 500 pub-goers and diners could have been contaminated with traces of the nerve agent used to poison Sergei and Yulia Skripal seven days ago. 

Speaking this afternoon, PHE's deputy medical director Dr Jenny Harries said "rigorous scientific analysis" had shown traces of the agent in The Mill pub in the Maltings and Zizzi on Castle Street. 

But Dr Harries said anyone who had been in either of the premises "can be reassured that this limited exposure will not have harmed their health to date". 

The panel would not answer questions on when evidence came to light that suggested a risk to a wider group of people, and said it had been part of an ongoing assessment process. 

And they would not answer when asked if they were confident that Zizzi and The Mill were the only locations that had been contaminated.

Dr Harries said the advice issued today was to prevent health risks that could develop in the future, if people had prolonged exposure to traces of the nerve agent, rather than any risk from exposure over the past seven days.

She suggested people wash their clothing and wipe down items such as mobile phones and wallets, but reiterated that general risk to the public is still considered to be low.

Temporary Chief Constable Kier Pritchard said the last week had been "unprecedented" as the county has "operated under the spotlight, with local to global interest". 

"Seven days ago today, my officers and staff responded to the initial call," he said. "Little did they know what they were dealing with, why would they?"

He praised the "first class" response from emergency services and paid tribute to all partners in the multi-agency response to the incident, "regardless of how big or small their role has been". 

CC Pritchard could not confirm how long police cordons at several city locations will remain in place, but said a "24/7 policing presence" would continue in the near future. 

Chief Fire Office Ben Ansell also praised his staff, and those of other services, and said he was "incredibly proud". 

He acknowledged that the public "may understandably be feeling unsure", and said: "It is important that the communities of Salisbury come together during this difficult time and I would like to reassure you all that we are working in a highly effective and coordinated way, with our partner agencies to bring the operational element of this incident to a successful, and above all, safe conclusion."