The two firefighters who died in the fire in Bicester, Oxfordshire, have been named as Jennie Logan, 30, and Martyn Sadler, 38.
David Chester, 57, also died after a massive fire ripped through a former RAF base.
Ten fire crews rushed to the inferno engulfing the Bicester Motion business park at 6.30pm on Thursday.
Workers at the former RAF Bicester, where several businesses restore classic cars and planes, were evacuated from the scene as neighbours heard multiple explosions and clouds of dense black smoke spread for miles.
In a statement on Friday evening, Thames Valley Police (TVP) said the families of the two dead firefighters and Mr Chester are being supported by specially trained officers.
Police said both firefighters worked at Oxfordshire Fire and Rescue Service and Mr Sadler was also part of the London Fire Brigade.
The force has launched an unexplained death probe but it is “currently not a criminal investigation”, Assistant Chief Constable Tim Metcalfe said.
Mr Metcalfe added “this is an absolute tragedy and my thoughts and the thoughts of everyone at Thames Valley Police are with the families, friends and colleagues” of the victims.
Two further OFRS firefighters suffered serious injuries and are currently in hospital, Oxfordshire County Council previously said.
The Lord-Lieutenant of Oxfordshire, Marjorie Neasham Glasgow, said the King would want to “pass on his sincerest condolences to all those affected”.
Members of the public started to lay flowers and tributes at the scene of the fire on Friday.
Three bouquets were laid under the Bicester Motion sign outside the former RAF base where a heavy police presence remains in place.
A handwritten note read: “Thank you for your service. Our hearts are with the services and families.”
The note featured hand-drawn pictures of an ambulance, police officer, doctor, and firefighter.
The flowers also include a handpicked bunch of daisies.
Prime Minister Sir Keir Starmer described the deaths as “devastating news”, adding: “The bravery of our firefighters is astounding. Hoping those in hospital make a full and swift recovery.”
Chief fire officer Rob MacDougall gave an emotional statement at the scene of the fire, saying: “I am immensely proud and grateful for the exemplary multi-agency response and the unwavering bravery demonstrated by all the emergency services personnel.”
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