Cannabis plants were found during a fire in Upton Park with the cause of the blaze a mystery.
The London Fire Brigade (LFB) called in the police at 5.15am on Monday, August 2 after the plants were discovered in the blaze in Thorngrove Road.
Officers visited the property but no arrests have been made and enquiries are ongoing, according to the Metropolitan Police.
Since then fire investigators have been unable to pin-point the cause of the blaze which destroyed the roof of the two-storey house.
A significant part of the first floor was also damaged. There were no reports of any injuries.
The cause has been recorded as undetermined following an initial probe by the LFB. This was due to the presence of the cannabis factory and subsequent police investigation.
It comes days after another cannabis factory in East Ham was raided by police.
Eight fire engines and about 60 firefighters fought the flames after the brigade was called at 5.02am.
Crews from Stratford, Plaistow, East Ham, Leytonstone, Dagenham and surrounding fire stations attended the blaze which lasted two hours.
The brigade was called at 5.02am and the fire was under control by 6.56am.
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