Authorities fear more people may have lost their lives in the blaze this morning on Redwood Grove.

Earlier it was announced three people, including a firefighter, had been injured.

Two of them suffered smoke inhalation and were taken to Bedford Hospital South Wing, while a third sustained leg injuries and was airlifted to Addenbrooke's Hospital.

The firefighter was one of those hurt by smoke inhalation, and they are now recovering at home.

Around 60 firefighters attended the scene, and teams described the blaze at the block of 20 flats as a "major incident".

The fire was so intense that it led to the collapse of the building's roof.

It is understood there was no main gas going into the property.

But firefighters investigating the cause of the blaze say their "working assumption is around gas" and they "can't rule out a heating stove or anything of that nature".

Bedfordshire Police Chief Superintendent John Murphy said it is possible more deaths will be discovered in the coming days as emergency services search the scene.

"Very sadly, we know that at least one person has passed away in the explosion today," Mr Murphy said.

"There is a possibility that there will be more fatalities discovered in the coming days as we continue to search through the scene and a number of people, as my colleague from the fire services has identified, were injured as well today."

'I saw someone jump from the second-floor window'

A local resident said they saw one person leap from a second-floor window to escape the burning block.

Pictures from the scene showed the three-storey structure on fire, and emergency services warned people to stay indoors and keep their windows and doors closed.

Adam Fisher, who works in a nearby building, said: "A huge explosion [was] heard - everyone went to our work car park to see what was happening.

"Our building is adjacent to the apartment complex - immediately an inferno (was) visible, huge smoke cloud billowing, people screaming and people frantically calling for emergency services."

Another witness, who did not want to be named, said: "I walked to town and saw the flames and also witnessed someone jump from the second-floor window whilst flames were blaring out."

'I just hope hardly anyone was in there'

Bali Mummon told Sky News: "You just kind of felt helpless at the time, thinking of the worst.

"The hope is people were not seriously injured - or even fatalities.

"And I don't know what's happened, but I just hope there was hardly anyone in there."

John O'Reilly, 76, was "knocked off [his] feet" by the explosion.

He added: "There were bricks in the road, so it was obviously a very large explosion to do that sort of damage."

The nearby John Bunyan Centre was set up as an emergency assistance centre, with members of the British Red Cross present to help.