A homicide investigation has been launched into the deaths of three family members after they ate a Christmas cake - believed to have been laced with arsenic - which also left an additional three hospitalised.

The family gathered for holiday celebrations on December 23 when they fell ill after consuming a Brazilian Christmas cake “Bolo de Natal” made by Zeli Terezinha Silva dos Anjos, 61, local media reports.

The baker fell sick herself after eating two slices.

Zeli Terezinha Silva dos Anjos and her sisters who both died from the cake. Photo / Facebook

But, her sister Maida Berenice Flores da Silva, 58, and niece Tatiana Denize Silva dos Anjos, 43, both suffered a cardiac arrest on Christmas Day, while her other sister Neuza Denize Silva dos Anjos, 65, was reported dead a day later.

The hospital said the cause of her death was “shock after poisoning”.

Great nephew Terezinha Silva dos Anjos, 10, and the baker remain in hospital, while another unnamed family member has been discharged.

Blood tests performed on a dead family member, and some surviving, found traces of arsenic, a toxic heavy metal, reported Brazilian television channel Globo.

Zeli Terezinha Silva dos Anjos' husband Paulo also died of food poisoning in September. Photo / Facebook

The incident has sparked an investigation into the death of Zeli’s husband, Paulo Luiz, who died from suspected “food poisoning” in September.

Local police have now requested to exhume his body as part of an investigation, the report added.

When questioned by police in hospital, the baker claimed she bought the ingredients on December 23.

However, investigators found expired food products in her home and an expired medicine bottle that contained a white liquid.

“A bottle was found, a medicine, which should have had capsules inside it and there were no capsules – there was a white liquid, and this white liquid will also be examined,” local police said.

The baker will be questioned again once she has been released from hospital.