Police were called to Indian Aroma on Woodford Avenue in Gants Hill around 9pm last night (August 22).
Officers arrived with the London Fire Brigade and London Ambulance Service.
Five people were rescued from the restaurant and suffered from burns and smoke inhalation.
They were taken to hospital by ambulance where three are in a critical condition.
Nine others were able to escape the restaurant before the fire service arrived.
There have been no arrests and an investigation is underway.
Detective Chief Inspector Mark Rogers, of the Met’s Central Specialist Crime North unit said: “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.”
A London Fire Brigade spokesperson said: “We were called at 2102 (22 August) 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.
“Around nine further people were able to leave the restaurant before firefighters arrived.
“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 2232.
“The cause of the fire is being investigated by the Brigade and the Metropolitan Police Service.”
A London Ambulance Service spokesperson said: “We were called at 9.04pm yesterday (22 August) to reports of a fire on Woodford Avenue, Ilford.
“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.”
Anyone with information is urged to contact the Met via 101, quoting 7559/22AUG.
If you wish to remain anonymous, you can speak with Crimestoppers on 0800 555 111.
