Guests at a hotel visited by two men suspected of carrying out the Salisbury nerve agent attack have been urged by health officials to come forward.
The chief medical officer for England said anyone who stayed at the CityStay Hotel in Bow, east London, between Sunday, March 4 and Friday, May 4 should contact the investigation team.
Dame Sally Davies said one of the "remaining issues of concern" for authorities is "identifying and reassuring those guests that stayed in the CityStay hotel in the period between the suspects leaving the hotel and the police identifying, controlling and testing this location."
"This room was only allowed back into use after experts deemed it to be safe," she added.
Police have issued domestic and European warrants for the arrest of Russian nationals Alexander Petrov and Ruslan Boshirov in connection with the Novichok poisoning of Sergei and Yulia Skripal in Salisbury in March.
They are believed to have stayed at the hotel on the nights of Friday, March 2 and Saturday, March 3.
Swabs were taken of the room the suspects stayed in which showed low level traces of Novichok but police have insisted that there was no risk to public health for people staying in the same room.
Dame Sally said she is "confident" that members of the public who travelled alongside the suspects between March 2 and 4, or after, are not at risk.
This includes those who travelled on public transport systems in London, train services and stations, airports, and those who were on the same Aeroflot flights.
"The risk to the public remains low - provided that our advice not to pick up unknown objects is followed," she said.
"Everyone can be confident that our public transport systems in London and the South are safe, and also we can be confident that Heathrow Airport, Gatwick Airport and the rail services linking them to London are safe."
Mayor of London Sadiq Khan said that he has been "assured" that there is "no risk to public health".
He added: "Furthermore, all levels of contamination found at hte hotel were below those that would cause concern for public health, as the police have made clear."
A statement from the CityStay hotel read:
Police have released details of the suspects movements and are urging anyone with information to contact them.
Assistant Commissioner of the Metropolitan Police, Neil Basu outlined details of a possible reconnaissance trip to Salisbury on the day before the attack.
The suspects movements are thought to be as follows:
- Arrived at Gatwick Airport at 3pm on Friday, March 2 having flown from Moscow on Aeroflot flight SU2588.
- They then travelled by train into London, arriving at Victoria station at 5.40pm.
- They travelled by public transport to Waterloo station and were in the area between 6pm and 7pm.
- They travelled to the City Stay Hotel in Bow Road, east London, where they stayed on Friday, March 2, and Saturday, March 3.
- On Saturday, March 3 they left the hotel and took the underground to Waterloo station, arriving at approximately 11.45am. They then caught a train to Salisbury arriving at 2.25pm.
- They are believed to have taken a similar route when they returned to London on the afternoon of Saturday, March 3, leaving Salisbury at approximately 4.10pm and arriving in Bow at approximately 8.05pm.
- On Sunday, March 4 the pair made the same journey from the Bow hotel to Waterloo at approximately 8.05am before continuing on to Salisbury.
- CCTV shows them in the vicinity of Mr Skripal's house where it is believed they contaminated the front door with Novichok.
- They left Salisbury and returned to Waterloo Station, arriving at approximately 4.45pm and boarded the Tube at approximately 6.30pm to London Heathrow Airport.
- From Heathrow Airport, they returned to Mosxow on Aeroflot flight SU2585, departing at 10.30pm on Sunday, March 4.
Police said there is no evidence that the suspects, who are members of the Russian military intelligence service also known as GRU, came back to the UK after that date.
Mr Basu said although the charges relate to the poisoning of the Skripals, he has no doubt that the incident is linked to that of Charlie Rowley and his partner Dawn Sturgess, who died after coming into contact with Novichok.
He said: "My thoughts remain with Dawn Sturgess’s family as they come to terms with their loss, the other victims who fell seriously ill after being exposed to a Novichok nerve agent and the people of Salisbury who have shown tremendous resilience throughout.
"Over the last six months we have meticulously followed the evidence, working closely with specialist forensic teams and scientists, as we have investigated both the attack on Sergei and Yulia Skripal in Salisbury, and the poisoning of Dawn Sturgess and Charlie Rowley. Let me be clear, we have no doubt these two incidents are connected and now form one investigation.
"Today’s announcement by the CPS marks the most significant development in this investigation.
"We now have sufficient evidence to bring charges in relation to the attack on Sergei and Yulia Skripal in Salisbury and domestic and European arrest warrants have been issued for the two suspects. We are also seeking to circulate Interpol Red Notices."
- Anyone with information should contact the investigation team in confidence on 0800 789 321 or email Salisbury2018@met.police.uk.