You can read their statements below.
I'm sure, like me, you are all shocked that we find ourselves talking about another Novichok nerve agent incident in the south of our county.
However, we've learned a vast amount from the first incident back in March and that has greatly informed our multi-agency response to the incident in Amesbury and Salisbury.
The communities here in Salisbury and in Amesbury have shown extraordinary resilience and spirit since the events of March 4 this year and I have no doubt they will rise to this latest challenge in the same way.
Our thoughts are with the two individuals who remain critically ill following their exposure to Novichok, their friends and families. This is, undoubtedly, a terrifying time for them all.
Since the incident in March, we've formed a close working relationship with our colleagues at the Counter Terrorism Policing Network and, as such, had very early conversations with them regarding this incident.
As you will all be aware, last night, the Counter Terrorism Policing Network confirmed they will be taking primacy for this investigation. They have also stated that they are not in a position to say whether the nerve agent used in this latest incident was from the same batch that Sergei and Yulia Skripal and Sgt Nick Bailey were exposed to back in March this year.
The possibility that these two investigations might be linked is clearly a line of enquiry for them but it is very important that we keep an open mind and do not speculate on this issue.
Although we are not leading this investigation, Wiltshire Police have a crucial role in supporting the Counter Terrorism Policing Network as their enquiries continue. This is a complex and fast-paced investigation and my officers, staff and volunteers are absolutely up to the task in hand.
Our top priority is, and will always be, the safety of everyone across our communities. To that end, people in Amesbury and Salisbury will see a significant increase in the amount of police officers there, which will include officers in protective equipment as they carry out activity at a number of sites. This will look similar to some of the activity which took place in Salisbury earlier this year.
I don't want people to be alarmed by this but reassured - we are there to support the ongoing investigation and provide a visible presence which we hope will help reassure our communities during this unpresented period. We are also there to answer any questions you might have and I would encourage you to speak to officers and staff who are at these sites across our county.
I would also like to reiterate that we have set up two phone numbers for anyone with concerns about this incident to call. These numbers are Freephone 0800 092 0410 or 0207 158 0124 if you are unable to access Freephone numbers.
These lines are being run jointly by Wiltshire Police alongside Public Health England colleagues. To date, we've taken more than 100 calls. Please use this number if you have any concerns or information relating to this incident. My staff are ready to receive your call.
Wiltshire Police continue to co-ordinate a large-scale multi-agency response to this major incident. We are working in conjunction with more than 12 partner agencies from health, local authorities in Wiltshire and Swindon, other blue light services, the military and governmental departments.
I fully appreciate the effect the cordons will have on local people and businesses. Please let me reassure you that my officers and staff, partner agencies and our colleagues at the Counter Terrorism Policing network will do all we can to progress this investigation and help return the communities of Amesbury and Salisbury back to normality.
You will now start to see protective barriers being put up to replace cordons at some of the scenes around Amesbury and Salisbury.
I want to reassure you that this is a request from Counter Terrorism Police and is simply to allow police officers and partners the space to carry out their investigation. Do not be alarmed.
I would ask that the public continue to respect these cordons.
We will be updating the public as much as we can but I need to re-emphasise that this is a complex and developing incident so it is difficult to know when these updates will be given.
Finally, as stated by the Counter Terrorism Police Network, I would like to reiterate the appeal for anyone with information in relation to this incident to contact police immediately.
Good Evening, I'm Angus Macpherson, the Police and Crime Commissioner for Wiltshire and Swindon.
The safety of the public continues to be of paramount importance to all agencies involved in this ongoing major incident.
To be in similar circumstances again is somewhat unimaginable.
This incident is receiving the full support of police and partner agencies in a coordinated major incident response.
It is important that the police investigation, led by the counter terrorism policing network, is able to proceed unhindered so the exact circumstances that led to these two people to fall seriously ill can be identified as quickly as possible.
My thoughts are with them and their families.
It is important to state that the information being issued by agencies involved has to be based on the available facts. The public will and must be updated as soon as possible once new information comes to light.
There will be an increased visible policing presence in and around Amesbury and Salisbury to provide reassurance to the public that the police, alongside partners and other emergency services, are doing all they can to support this investigation and return communities to normal.
Policing for this incident will be supported by a number of officers from other police forces and we are grateful for their support. This help enables Wiltshire Police to continue to provide business as usual policing across the county.
I recognise that this is a time of great anxiety and concern for those who live in the local area, and I would encourage anybody with concerns to check the Public Health England website for the latest advice or contact the dedicated phone line that has been set up by Wiltshire Police and Public Health England on 0800 092 0410.