Test results from the cake are expected to be available by next week, according to local media.

On Friday, police requested for the body of a man – the late husband of the woman who made the cake – to be exhumed. He died in September from food poisoning, but police said his death was deemed natural at the time.

She is not considered a suspect in either of these cases at this time, and investigations are ongoing.

Six out of seven people at the Christmas celebration ate the cake on Monday afternoon, including the woman who baked it.

Police told Brazilian broadcasters that she is the only one believed to have eaten two slices of her homemade cake, and her tests returned the highest levels of arsenic.

Speaking to local media, police chief Marcos Vinicius Veloso said some of the family members complained that the cake had a “peppery” taste.

The family then began to experience symptoms such as vomiting and diarrhoea, and five of them sought medical help at the Nossa Senhora dos Navegantes Hospital at around 01:00 local time (04:00 GMT) on Tuesday.

Hours later, two sisters died from cardiac arrest, the hospital said. They have been named in local media as Maida Berenice Flores da Silva, 58, and Tatiana Denize Silva dos Santos, 43.

The third victim, whose blood test presented traces of arsenic, died later on Tuesday evening from “shock after food poisoning”, the hospital said.

She has been named locally as 65-year-old Neuza Denize Silva dos Anjos.