The Food Safety Authority says it will call frozen foods manufacturer Talleys on Monday after a second case of black nightshade berries found in frozen peas.
One consumer found a handful of the potentially harmful berries in a peas and corn mix last week.
Another consumer, a father of preschoolers, says he complained to Talleys six months ago after finding almost as many nightshade berries as peas in a packet.
Humphrey Elton says that when he complained to Talleys, the company simply sent a $5 cheque and a letter saying the berries were not toxic.
The Food Safety Authority says almost 50% contamination is unacceptable and the authority will follow up the matter with Talleys.
The authority's director of compliance and investigation, Geoff Allen, says that proportion of contamination is unacceptable.
Mr Allen says most of the peas are contract grown and Talleys should be stipulating maximum levels of weeds and contaminants.
The National Poisons Centre says black nightshade can cause fever, vomiting and diarrhoea in small children if eaten in large quantities.