Brazilian police have arrested a woman facing charges of triple homicide after several members of her family were poisoned by an arsenic-laced Christmas cake, police said Monday.

Three women died and three other relatives fell ill after eating the cake during a family get-together on December 23 in Torres, a small seaside town in southern Brazil.

The police official in charge of the investigation, Marcos Veloso, told a press conference on Monday that there was "strong evidence" incriminating the family member who was arrested.

Her identity was not revealed by the police, but Brazilian media reported she was the daughter-in-law of the woman who prepared the cake.

Expert analyses found high levels of arsenic - a naturally occurring and extremely toxic element - in the victims' blood, the remaining slices of cake, and the flour used to bake it.

Veloso said the family members had noticed a "spicy" and "unpleasant" flavor to the cake. The woman who baked the cake asked them to stop eating it, but it was too late.

Six relatives were hospitalized. Two sisters, aged 58 and 65, as well as the 43-year-old daughter of the eldest sister, died within hours of each other.

The third sister, aged 61, who prepared the cake, is still in hospital in stable condition, according to the latest medical update.

The husband of one of the deceased sisters and a 10-year-old boy - whose mother and grandmother were among those killed - have since been discharged.

Forensic police director of the southern state of Rio Grande do Sul, Marguet Mittman, said that "very high concentrations of arsenic were found in the three victims."

"To give an idea, 35 micrograms are enough to cause the death of a person. In one of the victims there was a concentration 350 times higher," she said.

As for the motive behind the deadly cake, Veloso said the family had a "very harmonious" relationship but with long-standing "differences" that could explain the origin of the crime.

The police have also requested the exhumation of the body of the late husband of the woman who prepared the cake. His death last September was attributed to "food poisoning", and was not investigated.

AFP

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Brazil police arrest woman over deadly arsenic cake