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Autopsies on Noelene and Yvana Bischoff (R), who died mysteriously in Bali, have been completed.

The Bischoff family believe they're still weeks from discovering why Noelene and her teenage daughter Yvana died in Bali.

Their bodies were released on Wednesday following the completion of autopsies in Queensland.

Noelene's brother Malcolm Bischoff says the family isn't sure how long the coroner's investigation will take, but was initially told it would be two to four weeks.

"They've been tight-lipped on that, probably because they don't want to give us false hope," he told AAP.

The pair became violently ill and died less than a day after checking in at the Padang Bai resort.

Their Indonesian death certificates state both had heart attacks, Mr Bischoff said, and there has been speculation toxic fish caused them to fall fatally ill.

Mr Bischoff doesn't want to guess what's responsible, but says the pair had no known allergies and food poisoning theories don't quite add up.

"To me it's just a bit bizarre," he said.

"I wouldn't like to speculate."

While the Bischoffs are anxiously waiting to find out what caused the deaths of Noelene and Yvana, they are relieved they can now prepare to say goodbye.

"We are relieved they have released their bodies so we can finally put them to rest - that's half the battle," Mr Bischoff said.

"It's been hard. It still is because we had a week of uncertainty with the bodies and what's happening."

A service for Noelene and Yvana will be held at the Gatton Baptist Church on Monday.

"Originally we were going to have a grave side service, but we've had such a response from people wanting to attend a full service," Mr Bischoff said.

Many of Noelene's relatives and friends still reside in Gatton, west of Brisbane, where she grew up.

Mourners will also travel to the service from the Sunshine Coast, where the mother and daughter resided.

The service begins at 11.30am (AEST).