People should avoid making and eating foods with fermented rice and flour, the National Health Commission said on Tuesday.

The commission released the public reminder after nine family members in Jixi city, Northeast China's Heilongjiang province, died after eating homemade corn noodles.

During a 12-member family gathering on the morning of Oct 5, nine older family members ate suantangzi, a thick noodle made from fermented corn flour. Three young people present refused to try the food because of its strange taste, according to the local government.

The nine who ate the noodles fell ill several hours later and eight were confirmed dead as of Oct 11, while the only survivor - a 47-year-old woman surnamed Li - received treatment in a hospital. Li died at noon on Monday, according to her son.

A high concentration of bongkrekic acid, a respiratory toxin produced by the bacterium pseudomonas cocovenenans, was detected in the noodles as well as the gastric fluid of those who became ill, the provincial health commission said on Oct 12.

Bongkrekic acid is a main cause of poisoning from fermented flour and rice products and spoiled white fungus, as well as other spoiled starch products, experts said. 

Eating food contaminated with bongkrekic acid can result in poisoning for both humans and animals and even lead to death, with death rates as high as 40 to 100 percent.

Using fresh and unspoiled food materials and frequently changing water when making food can reduce the risk of contamination, but it is best to avoid making and ingesting foods made of fermented grain entirely for safety concerns, according to the commission.