Russia has cracked down on McDonald's this month, closing three other branches of the hugely popular burger chain over alleged hygiene violations in a move widely seen as a retaliation against Western sanctions over Ukraine.
McDonald's said in a statement that 12 restaurants have now been closed by the authorities, seven of them in southern Russia, and "currently more than 100 inspections are being carried out".
The company said it is looking at the alleged violations to work out how to reopen the restaurants as soon as possible.
In the latest development, a spokesman for Russia's food safety agency in the central Yaroslav region, cited by the RIA-Novosti news agency, said that E coli, some strains of which can cause serious food poisoning, had been found in iceberg lettuce in one restaurant.
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McDonald's has over 400 restaurants in Russia with more than 37,000 employees. It opened the first in central Moscow during the late Soviet era, attracting giant queues of customers eager to try US fast food for the first time.
Russia has a long history of using sudden food safety concerns as a political weapon against unfriendly states.
While McDonald's is a symbol of American culture, the company has made huge efforts to build up its local supply chain and says it buys 85 per cent of the food it serves in Russia inside the country.