Thirteen members of the same family have died in Namibia after eating porridge that authorities believe became toxic when it was mixed with a fermented substance left over from a homemade alcoholic beverage, the health ministry and the state broadcaster reported.

The Namibian Broadcasting Corporation said another four people are in a critical condition in the hospital. NBC, quoting the Namibian health ministry, said at least 20 people consumed the "poisonous or toxic" porridge after it was mixed with sediment from a homemade beer.

The victims ranged in age from 2 to 33, the ministry said. The incident happened in the Kavango East region in the far northeast of the country.

"All patients are being monitored closely," the health ministry said in a statement, adding that additional blood samples were taken for alcohol poisoning testing.

The health ministry also said it had "deployed a team of social workers to provide psychosocial support and counselling to the bereaved family."