A vehicle recovery centre is being searched as part of the latest investigation into the nerve agent attack on a former Russian spy.
It is believed the building was searched overnight as Sergei Skripal's maroon-coloured BMW is inside.
Former double agent Mr Skripal, 66, and his daughter Yulia, 33, remain in "a very serious condition" in hospital after they were found slumped on a park bench in Salisbury on Sunday evening.
DS Bailey is believed to have been the first person at the scene, although there are now suggestions he may have become ill after retracing Mr Skripal's steps from his home in Salisbury.
Sky News' crime correspondent Martin Brunt said there are suggestions police believe the spy, his daughter and DS Bailey were poisoned at the Russian's home.
Tom Tugendhat, chairman of the Foreign Affairs Select Committee, has said all the evidence points to the nerve agent attack being ordered by the Kremlin.
Home Secretary Amber Rudd, who yesterday called the attack "brazen", visited the scene in Salisbury and spoke to investigators this morning.
Mr Skripal served four years of a 13-year sentence in Russia after he was caught spying for MI6 and was released as part of a spy exchange in 2010, when he was given refuge in the UK.
Images have emerged today of Mr Skripal in Malta in 1985.
A source close to the the Maltese foreign office confirmed to Sky News that Skripal was stationed to Malta in 1985 and served into the early 1990s as Cultural and Sports Attache within the Soviet Embassy in Malta.
After he and his daughter were found the first area to be cordoned off was Zizzi's Italian restaurant in central Salisbury, where the pair dined on Sunday.
On Thursday, police revealed 21 people had been treated in public, including emergency service workers and members of the public.
Officers also widened the search area, placing forensics tents in front of and at the rear of Mr Skripal's home.
They have also begun a fresh fingertip search of the house.
Sky News' West of England correspondent, Rebecca Williams, said there was a lot of activity at the house and that it was a fast-moving investigation.
She added that police are focusing on identifying a man and a woman seen yards away from where the pair collapsed.
There is also a cordon around the graves of Mr Skripal's son, Alexandr, and his wife, Lyudmila, who died in suspicious circumstances in 2017 and 2012 respectively.
So far there is no indication any bodies could be exhumed but it could be part of the investigation, Sky News understands.
Detectives have not yet revealed what kind of chemical was used.
But experts believe any possible compounds used "are part of a type of chemical agent made specifically for warfare", counter-terrorism expert Andy Oppenheimer told Sky News.
Russian exile Valery Morozov told Sky News Mr Skripal had been in contact with the Russia and visited its London embassy once a month.
Prime Minister Theresa May said her thoughts were with all the victims, and praised the response of the emergency services.
She said the incident was "a stark reminder, if ever one was needed, of the dangerous situations our emergency services face and the dedication and courage they display every day in order to keep us safe".
The Home Secretary threatened a "robust" response to the "brazen and reckless act" committed on UK soil.
Ms Rudd said the poisoning "was attempted murder in the most cruel and public way".
While she said speculation must be avoided, she said "people are right to want to know who to hold to account".
She said the Government is "committed to doing all we can to bring the perpetrators to justice – whoever they are and wherever they may be".
The Kremlin has insisted it is not involved, and said any allegations are a plot to whip up anti-Russian sentiment.
More from Salisbury spy
President Vladimir Putin has yet to respond to the news that nerve agent was involved in the poisoning.
:: Watch a special report about the Salisbury spy poisoning on Sky News at 2.30pm, 4,30pm and 6.30pm.