The deaths of Sunshine Coast mother Noelene Bischoff and her 14 year old daughter were most likely caused by a rare and devastating combination of food poisoning, lingering asthma and migraine tablets.
The family met with coronial authorities from Queensland yesterday afternoon and were briefed on potential causes of death.
Noelene's brother Malcolm said that the Coroner was "95 per cent" sure that it was scombroid poisoning, a form of food poisoning found in fish that was extremely rare.
"It's a very rare thing ... that comes from fish," Mr Bischoff said. "That, and with signs of asthma is a very lethal combination."
While on a summer holiday in Bali a month ago the pair became violently ill after eating fish at a restaurant only hours before they died.
While more tests would be carried out in the coming weeks, authorities had ruled out any foul play.
"It was a one in 20 million chance for two people to be affected by it," Mr Bischoff said.