Two firefighters who died in a blaze at an Oxfordshire business park have been named as Jennie Logan and Martyn Sadler, while a member of the public who died is David Chester.
Ms Logan, 30, Mr Sadler, 38, and Mr Chester, 57, from Bicester, died after explosions were heard at Bicester Motion – a former RAF base – on Thursday.
Both firefighters worked at Oxfordshire Fire and Rescue Service and Mr Sadler was also part of the London Fire Brigade, Thames Valley Police said.
Two more firefighters sustained serious injuries and remain in hospital, Oxfordshire County Council said.
The fire was reported at about 18:30 BST on Thursday and rapidly spread through a former aircraft hangar at the site.
At its height, 10 fire crews were tackling the blaze.
The police have launched an unexplained death investigation, but are not currently treating it as a criminal matter.
Assistant Chief Constable Tim Metcalfe described the deaths as "an absolute tragedy" and said the thoughts of everyone at the force were with the families, friends and colleagues of those who had died.
Officers will remain at the scene for a number of days to ensure the public remain safe.
At the scene on Friday, a visibly emotional Chief Fire Officer Rob MacDougall said he spoke with "a heavy heart" when he confirmed the deaths.
He added: "Our thoughts are with the family friends and colleagues affected during this time.
"I'm immensely proud and grateful for the exemplary multiagency response and the unwavering bravery demonstrated by the emergency services personnel."
London Fire Commissioner Andy Roe described it as an "incredibly challenging day" for UK fire services and said it highlighted the high-risk nature of their work.
He said: "This is clearly an incredibly difficult time for us all; we have lost a well-respected and much-loved colleague who exemplified courage and selflessness in the service of others.
"Our thoughts are with all the families, friends, and colleagues impacted by this tragedy. We are doing everything we can to provide support to Martyn's family and colleagues."
He added: "Our sincere condolences go out to Oxfordshire Fire and Rescue Service who also sadly lost a firefighter at this incident, with a further two colleagues in hospital."
