In Salisbury, the investigation continued to move at a fast pace.
For experts in chemical, biological and nuclear warfare, even seemingly simple tasks are complex and risky.
Detectives are retracing the movements of former Russian spy Sergei Skripal and his daughter Yulia before they collapsed from nerve-agent poisoning, as they try to discover how the toxin was administered and where it was manufactured.
A witness said he saw police searching a auto at a vehicle recovery centre close to Mr Skripal's home on Thursday, describing seeing around 10 people in hazmat suits looking at the Mercedes people carrier. Researchers have also speculated the substance came from a state laboratory.
Defence Secretary Gavin Williamson said the armed forces "have the right people with the right skills" to deal with the "crucial inquiry". "This is a awful incident and my thoughts remain with the victims and their families".
Police officer Det Sgt Nick Bailey, 38, who was admitted to intensive care after the incident is said to be in a "stable and conscious" condition.
The investigation into the poisoning of a Russian double agent and his daughter intensified Friday, with Britain deploying military personnel to assist with the probe.
Home Secretary Amber Rudd said after the meeting it was still "too early" to say with certainty who was behind the poisoning that left former Russian military intelligence agent Sergei Skripal and his daughter in critical condition.
A British police officer who responded to the scene was also seriously injured, but was "talking and engaging" as of Thursday morning.
"At the moment our priority is going to be the incident, which is why I'm here in Salisbury today, making sure that everybody's protected around the incident, making sure the emergency services have had the support that they need and will continue to get it".More news: Labour suspends party members in antisemitic Facebook group
Skripal, a retired Russian military intelligence colonel, was one of four prisoners released by Moscow in 2010 in exchange for 10 Russian sleeper agents in the United States, as part of a swap which included high-profile spy Anna Chapman.
"We have not heard a single fact; we only watch footage on TV, where our colleagues say with serious faces and with gusto that if it is Russian Federation, then a response will follow that Russian Federation will remember forever", he said, according to Interfax.
Which is why the unusual circumstances led to the counterterrorism unit getting involved as well as warnings from Boris Johnson if the Kremlin does get linked to the suspected nerve agent used on Skripal.
The operation on Saturday focused on the cemetery where Mr Skripal's wife and son are buried.
Lyudmila Skripal died of cancer in 2012. It has denied any involvement in Litvenko's death or the attempt on the Skripals' lives. At the cemetery, forensic tents were placed over the graves of Mr Skripal's wife and son.
Sources close to the investigation believe the chemical agent used is probably something other than Sarin or VX, the BBC reported.
In 2006, Skripal was convicted in Russian Federation of being a double agent and secretly passing classified information to British intelligence.
Mr Skripal's house and his auto have also been cordoned off.
Investigators are looking at the possibility that the attackers flew into Britain to carry out their mission and then left, possibly individually, afterwards.