The limb was spotted in the Regent's Canal in Hackney by a British Waterways employee on Monday - two weeks after the 29-year-old's mutilated body was found.
Divers have been searching the water in a bid to find her remaining missing body parts.
A Scotland Yard spokesman said: "Police were called at 9.35am yesterday to reports of an arm found in the Regent's Canal in Hackney.
"Officers attended and recovered the limb close to the Broadway Market stretch of the canal.
"We await further tests to determine identity, but at this stage it is believed to be connected to the murder of Gemma McCluskie." Read More