Four fire engines and 21 firefighters were called to a flat fire on Stamford Hill in Hackney.
The blaze badly damaged a flat on the second floor of a five storey block.
Four men were taken to hospital by London Ambulance Service crews. One man sadly died later in hospital.
The police are appealing for information and witnesses.
Detective Inspector Paul Ridley from Hackney CID said, "An investigation has been launched to establish the circumstances of this incident. I would request that anyone who can provide any further information, who witnessed the explosion or the immediate aftermath to contact my investigation team."
Anyone with information is asked to call Hackney CID on 101 or Crimestoppers anonymously on 0800 555 111 or at crimestoppers-uk.org.
The Brigade was called at 1433 and the fire was under control by 1612. Fire crews from Hornsey, Leyton, Tottenham and Walthamstow fire stations attended the incident. The cause of the fire is under investigation.