One man has died and another resident is critically injured after a fire and explosion at Woodlands View care home in Stevenage, Hertfordshire on Saturday.
Hertfordshire County Council said there had been a "minor explosion" caused by an oxygen cylinder.
A resident in his 80s who was in the room where the fire started died in hospital. Another resident is in a critical condition and five others are being assessed in hospital.
The home in Magpie Crescent is owned by HC-One. A spokesman said: "Our deepest sympathies are with their family and we are doing everything we can to support them.
"Staff at the home took immediate action to notify the emergency services and evacuate residents, staff and visitors to safety in other parts of the home."
The company added that affected residents had been moved to other buildings at the site and to "nearby sister homes".
A Hertfordshire County Council spokeswoman said: "There appears to have been a minor explosion caused by an oxygen cylinder but a full investigation will need to be carried out to confirm this."
Hertfordshire's chief fire officer Darryl Keen said an investigation was under way and added: "The fire was largely contained to the one room but there was a lot of smoke, which caused difficulties in some of the residents leaving the building."
Eight fire engines, six ambulances and two air ambulances were sent to the scene. The fire was under control and all residents were evacuated from the building.
The care home, acquired by HC-One in August 2017, is a complex of six separate buildings with about 25 residents in each unit.
An inspection by the Care Quality Commission (CQC) in June, when the home was owned by Bupa, found it "required improvement" in all areas including safety.
The CQC report said: "People's individual risks were assessed, however, this was not consistent and some needs were not risk assessed."
However, the report added the buildings "all had key-coded doors and fire exits were linked to the fire alarm so that they unlock in the event of the alarm sounding".
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