The Independent understands that units from the Army, RAF and Navy are being deployed alongside experts in chemical, biological, radiological and nuclear (CBRN) warfare.
Five days after police said they were "targeted specifically" with a nerve agent, Sergei Skripal, 66, and his daughter Yulia, 33, remained in critical condition in the quiet English city of Salisbury. Researchers have also speculated the substance came from a state laboratory.
Defence Secretary Gavin Williamson said Thursday that Russian Federation was "becoming an ever-greater threat".
"We have the right people with the right skills to assist with this crucial inquiry", Williamson said. "This is a awful incident and my thoughts remain with the victims and their families".
Britain was to hold a second meeting of its national emergencies committee on Saturday in response to a nerve agent attack on a Russian former spy.
Police also extended the cordon around the modest suburban home of Sergei Skripal in Salisbury, as Home Secretary Amber Rudd visited the city, calling the attack "outrageous".
He said: "There obviously are some indications the officer, and I'm very sorry that he has been injured, has actually been to the house, whereas there was a doctor who looked after the patients in the open who hasn't been affected at all".
However, he said, "there are not 101 likely offenders", apparently a reference to the difficulty in producing nerve agent, which would limit the number of suspects with the ability to carry out the attack.
Skripal, a former Russian military intelligence officer, was convicted in 2006 of spying for Britain and released by Moscow in 2010 as part of a spy swap.
"As both the Prime Minister and Home Secretary have said, if a state actor is found to be responsible, there will be an appropriate response".
"The use of a nerve agent on United Kingdom soil is a brazen and reckless act - this was attempted murder in the most cruel and public way", Rudd said.
Police sealed off the gravestone of Skripal's wife Liudmila, who was buried in 2012, and the memorial stone of his son, Alexander, who was cremated previous year, the UK's Press Association reported.
They are located at separate sites in the London Road Cemetery with each guarded by a police officer.
Lyudmila Skripal died of cancer in 2012. Sky News reported that policemen in chemical protection suits took away flowers from the grave of Skripal's wife and son in Salisbury, which the poisoned relatives had brought there shortly before the incident.
The former double agent may have become a target after using his contacts in the intelligence community to work for private security firms, investigators believe.
"Investigation of Sergei Skripal case follows the Litvinenko script: most info to be classified, Russian Federation to get no access to investigation files and no opportunity to assess its credibility", the tweet says.
Lord Blair, a former Met Commissioner, suggested on the BBC's Today programme the seriously ill detective had visited Mr Skripal's home.