Some 200 people suffered from a gastroenteritis epidemic in the Helsinki metropolitan area of Finland after eating food supplied by a catering company, media reported on Thursday.

Eeva Ruotsalainen, deputy director of the Hospital District of Helsinki and Uusimaa (HUS), told the Finnish daily Helsingin Sanomat that most of the infections occurred in festive occasions arranged in Helsinki about two weeks ago, and some others occurred in Espoo, Vantaa and Kauniainen after the events.

Laboratory results showed that more than 80 of the patients were infected by EHEC (Enterohaemorrhagic Escherichia coli) which include Shiga-toxin producing E. coli. said Finnish National Institute for Health and Welfare.

Officials contacted patients of high-risk groups, such as children under the age of five, elderly people, pregnant women and persons who work in the food industry.

Health officials suspected that the infection originated from an Espoo-based catering company which provided food services for the events.

Finnish national broadcaster Yle reported that the source of the epidemic was traced to rucola or rocket salad sold by Kesko, a major retailer of Finland.

Matti Kalervo, vice president of Kesko, told Yle that the rucola in question was grown in Denmark and packaged in Sweden. The breakout of the epidemic was caused by a single batch of rucola exclusively for industrial kitchens. Kesko has started to perform microbiological tests on the product, said Kalervo. EHEC bacteria, a subtype of Escherichia coli, can cause human hemorrhagic colitis. The infection of EHEC can lead to hemolytic uremic syndrome, which in turn may cause permanent kidney damage or even death.