The number of those affected has also risen to 38, SSI said.
The outbreak has been traced to the deli meat rullepølse produced by the company Jørn A. Rullepølser, which has been shut down.
A total of 30 products – including variations of rullepølse, salami and hot dogs – were recalled.
The Danish Veterinary and Food Administration (Fødevarestrylsen) also warned on Monday of a listeria risk in halibut sold by the company Hjerting Laks that was sold in Netto, Irma and Føtex stores.
Fødevarestrylsen was criticised for not acting quickly enough in responding to the listeria outbreak, with the food and agriculture minister, Dan Jørgensen, saying that “serious mistakes” took place.