Subway Japan Inc., the Japanese affiliate of the major U.S. sandwich chain Subway Restaurants, has stopped selling sandwiches after its import dealer learned that the bread dough contains an enzyme derived from unauthorized genetically modified microorganisms.

Subway reported the findings to the Tokyo Metropolitan Government and stopped selling sandwiches on Friday, Tokyo government officials said.

The metropolitan government will investigate the case in accordance with the Food Sanitation Law.

The officials said Subway used four types of frozen bread dough containing an enzyme not approved by the Ministry of Health, Labor and Welfare.

The dough was imported from a dealer in New Zealand by Sumitomo Corp., which delivered all of its imported dough to Subway.

Subway Japan operates more than 90 outlets in the greater metropolitan area and the Kinki region of western Japan.