Two people have been arrested on suspicion of arson with intent to endanger life after a fire at a restaurant in Ilford.
A 15-year-old boy and a 54-year-old man have been arrested following the suspected arson attack.
Three women and two men were injured in the incident, with two of them in a life-threatening condition.
It is also believed there are an additional two victims who left the scene before officers arrived, the force said.
Detective Chief Inspector Mark Rogers, of the Met's Central Specialist Crime North unit, said: "While we have made two arrests, our investigation continues at pace so we can piece together what happened on Friday evening.
"I know the community is concerned and shocked by this incident.
"I would urge anyone with any information or concerns to come forward and speak to police."
Anyone with information is urged to contact the Met via 101, quoting 7559/22AUG.
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The incident occurred in Ilford, London
| Google MapsThe force added that if you wish to remain anonymous, speak with Crimestoppers on 0800 555 111.
The alleged arson attack occurred on Friday evening, with paramedics being called at 9.04pm to reports of a fire on Woodford Avenue, Ilford.
A spokesman for the London Ambulance Service said on Friday: "We sent resources to the scene, including ambulance crews, an advanced paramedic, an incident response officer and paramedics from our hazardous area response team.
"We also dispatched a trauma team in a car from London's Air Ambulance.
"We treated five people for burns and smoke inhalation. We took two patients to a major trauma centre and three others to local hospitals."
A London Fire Brigade spokesman added: "We were called at 9.02pm to reports of a fire at a restaurant on Woodford Avenue in Gants Hill.
"Part of the ground floor restaurant was damaged by fire. Firefighters wearing breathing apparatus rescued five people from the restaurant. They were all taken to hospital by London Ambulance Service.
"The Brigade's Control Officers received seven calls about the fire and mobilised crews from Ilford, Hainault, Leytonstone and Woodford fire stations to the scene. The fire was extinguished by 10.32pm."
Wes Streeting offered his thanks to emergency personnel
| PALocal MP and Health Secretary Wes Streeting offered his thanks to service personal for their response to the "serious" incident on Friday.
Detective Chief Inspector Mark Rogers, of the Met's Central Specialist Crime North unit, said on Friday: "We understand this incident will cause concern within the community.
"My team of specialist detectives are working at speed to piece the incident together.
"Locals can expect to see a large police presence in the area. If you have any concerns, please speak to those officers on the ground."