The Consumer Affairs Agency plans to question by the end of this week the president of a company that sold traditional New Year's food packages through the Groupon website, according to agency officials.
A number of people who bought boxes of the assorted "osechi" foods have complained the items delivered to their homes were not consistent with those shown in a picture on the Groupon site.
The agency said Friday it is looking into the matter for a possible violation of a law against misleading representations in product sales.
The Kanagawa Prefectural Government and the farm ministry are also assessing whether the sales are subject to a law on food labeling.
According to the Yokohama Municipal Government, the Yokohama-based seller, Food Culture Research Institute, has received reports that several buyers experienced health problems after eating the items.
Groupon is becoming increasingly popular for its huge website discounts.