The outbreak in Västra Götaland has been linked to ready meals with potatoes from Food Company i Lidköping AB.
Listeria was detected in the environment and on the machine at the production site used to distribute mash potatoes.
The company is continuing to operate but with restrictions on items they produce, including no mashed potatoes, and all batches are tested.
It recalled products under the brands Kinnevikens mat and Lillesjö from the market with dates 16, 17, 18, 19, 22, 23, 24 and 25 May.
Older people affected and underlying illness
Swedish names of recalled products
Köttbullar med lingon, gräddsås, bönor och potatismos; Nötköttbullar med lingonsylt, gräddsås, bönor och potatismos; Spätta med champinjonkräm, spenat samt potatis; Fisksymfoni med dillsås och räkor, serveras med potatismos; Torsk med dillsås och räkor, serveras med potatismos; Mandelbakad fisk med dillsås, citron, ärtor och potatismos and Kalvfärsbiff med lökfrästa ärtor, gräddsås, potatismos och lingon
Six confirmed cases and one suspected illness occurred between February and early May. All those that died had underlying illness so it is not known if listeriosis was responsible.
Cases are between 59 and 84 years old and live in Västra Götaland, a county in Western Sweden.
As Listeria is killed when products are heated to 70 degrees, the outbreak was caused by cooking error and cases tended not to eat the whole portions at once.
Livsmedelsverket (National Food Agency) told us that interviews with cases did not reveal a common source.
The key to finding the source was samples of ready meals from the freezer at the home of one of the cases, which were positive.
The agency added there may be more cases because of the long incubation period of Listeria.
Samples of ready meals showed the same variant of Listeria serotype IVb as in the patients. This serotype is not common in the country.
Mash machine discarded
Environmental health in Lidköping inspected Food Company in Lidköping AB without any remarks regarding hygiene routines.
In connection with the inspection, they also took samples of a number of products, equipment and in the premises. Results from the factory are pending.
Food Company i Lidköping AB said the contaminated machine used to distribute mash potatoes is no longer in the factory.
The company added it will implement measures to prevent a repeat of the incident.
In addition to regular tests, it will take samples on products, staff and in the production room to ensure the bacteria is no longer in the plant until it can confirm the risk is finished.
The firm urged customers who bought any of the products with dates mentioned to return them to the store to get their money back.