A Queensland mother and her teenage daughter who fell fatally ill in Bali were unlikely to have seafood allergies, their family says.
Relatives of Noelene Bischoff and her 14-year-old daughter Yvana have been told toxic fish may have caused their deaths.
However, Noelene's brother Malcolm Bischoff says the family doubts that's the case.
"There is a bit of speculation about food allergies or seafood allergies which I don't believe is true because I've had seafood with my sister on a number of occasions,'' Mr Bischoff told Channel Seven's Sunrise program.
"The thing we are sort of questioning is that from when they actually appeared to get sick they were both dead within five hours.''
A hotel manager had also contacted the family to say he felt fine after eating the fish dish that night, Mr Bischoff added.
Medicine found in Noelene and Yvana's hotel room is being tested in bid to determine the cause of their deaths.
But Mr Bischoff said that's likely to be standard medication holidaymakers take to Bali.
"They weren't on any major medication either of them,'' he said.
Ms Bischoff, a senior nurse from the Sunshine Coast, and Yvana died in the early hours of Saturday, less than a day after they checked into a beachfront resort on Bali's east coast.
Padang Bai Beach Resort staff were alerted early on Saturday morning when Yvana asked for help, telling security guards she and her mother had fallen gravelly ill.
An ambulance took them to a nearby medical centre but the mother died about 1.45am local time, local sources say.
The girl was rushed to BIMC Hospital, an international clinic in Denpasar, but could not be saved.
Mr Bischoff said the family was struggling to come to terms with the tragedy that they believe doesn't add up.
"We would really like to have some answers ... because there are a few things that are a bit bizarre about the whole situation we feel,'' he said.
Indonesian officials say they are yet to perform an autopsy on the mother and daughter as they are waiting for permission.
Under Indonesian law, an autopsy can proceed without permission from Tuesday.
Mr Bischoff says the family is waiting to hear from the Department of Foreign Affairs and Trade to make arrangements for the bodies.
Queensland Attorney-General Jarrod Bleijie is a friend of the Bischoff family and says the tragedy has left the Sunshine Coast community reeling.
"I think it's tragic news for any family to hear particularly when it happens in foreign land,'' Mr Bleijie told ABC Radio.
"On behalf of the Sunshine Coast community I express our absolute condolences.''