The Food and Environmental Hygiene Department is investigating whether products from an M&M Mars factory in Chicago, which was shut down last week due to hygiene problems, were on sale in Hong Kong.
The Chicago Public Health Department ordered the factory shut after the company failed to rectify problems found during a previous inspection. The plant manufactured many of M&Ms popular products, such as Snickers, Milky Way and Mars bars.
Chicago health inspectors had found mouse faeces and fruit flies in the production and storage areas of the factory.
However, M&M's Hong Kong agent, Effem Foods, said that products sold in the city were not sourced from the Chicago plant.
Both ParknShop and Wellcome said that the closure of the Chicago plant would not affect their stock.
Meanwhile, snack manufacturer Aji Ichiban said its range sold in Hong Kong was safe after tests on one of its products sold on the mainland was found to have high amounts of preservatives.