Please find below the following statements from Wiltshire Police, which were read during a press conference in Devizes at 3pm today.
Police and Crime Commissioner for Wiltshire and Swindon Angus Macpherson said: "It is particularly shocking that an incident such as this appears to have taken place on a quiet Sunday afternoon in the cathedral city of Salisbury.
"I have been briefed by the Chief Constable and can say with confidence that the matter has received the full support of police and partner agencies in a coordinated major incident response.
"I can also say that the measures necessary to ensure the safety of the public in and around the scene have also been taken."
Temporary Chief Constable of Wiltshire Police Kier Pritchard said: "As you are aware, we declared a major incident yesterday after a man and a woman were taken seriously ill in Salisbury on Sunday. They both remain in a critical condition in hospital and our thoughts and best wishes are with their families during this difficult time
"A full multi-agency response was activated and currently involves Public Health England, the NHS, Local Authorities both in Swindon and Wiltshire and a range of other key partners.
"This has been a fast paced investigation and our focus has been on trying to establish what has caused these people to become critically ill and whether or not any criminal activity has taken place.
"Since Sunday, we have had access to a wide range of specialist resources and services that have been working alongside us.
"You will be aware that this afternoon, the Metropolitan Police have confirmed that, due to the unusual circumstances, the Counter Terrorism network will now be leading this investigation, as it has the specialist expertise to do so.
"It is important to reiterate that they have not declared it as a terrorist incident and at this stage they are keeping an open mind as to what happened.
"The advice from Public Health England remains that, based on the evidence to date, currently there doesn't appear to be any immediate risk to the public.
"We can confirm that a small number of emergency services personnel, including some police officers and staff, were assessed immediately after the incident.
"I would like to sincerely thank members of the public for their continued assistance and for respecting the cordons which remain in place in and around the Salisbury area.
"I would also like to thank our partners, staff from supporting agencies and our officers, staff and volunteers for their dedication and hard work over the last few days.
"I fully understand the concerns that many of our residents in Salisbury and across the wider county may be feeling today and I want to again reassure you that there does not appear to be any immediate risk to the public.
"During this time, it is vital that we continue to provide an increased policing presence in the Salisbury city area as this plays an important part in helping to reassure our communities."