A 24-year-old man was arrested after a hand gun with live ammunition and 11.5kg of heroin were found in a car in Fakruddin Street in Bethnal Green.
Officers also searched his home during the raid last Wednesday and recovered £12,000 in cash.
The man was bailed pending further enquiries.
DI Iain Harkes, of Tower Hamlets Police, said: “This is one of many successes within Tower Hamlets and has resulted in a potentially lethal firearm and a substantial amount of drugs being taken of the streets.
“I would urge anyone who has information about firearms or drugs in their community to contact police.”
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