TWO YOUNG Swedish tourists have died in a Krabi holiday bungalow mystery in circumstances that may not be resolved until a second autopsy has been performed on their bodies.

The remains of a young man, aged 25, and his 23-year-old female companion have been repatriated to Sweden as police investigations continue in Sweden and in Thailand.

The investigating police officer in Krabi confirmed today that the deaths of the Swedish couple took place on April 2 at a holiday bungalow in Ao Nang, a popular seaside village that is the gateway to many other Krabi islands and beaches.

''Not many cases happen here like this,'' he said.

According to the Swedish newspaper Aftonbladet, the dead couple had been travelling with another couple from the same village in Sweden for about a week and they intended to holiday around Asia until June.

The other couple have cut short their trip to return to the Swedish district of Jamtland.

Police in Krabi are now awaiting the results of autopsies that were performed on the dead couple at Prince of Songkhla Hospital in the southern Thai city of Had Yai.

The first doctor at the scene attributed the death of the couple to electrocution as they shared a shower in a twin room at the bungalow. But the owner of the bungalow has since rejected electric shock as a possible cause.

The couple were found naked in the shower alcove, the woman dead under the stream of water, with the man nearby and barely conscious but breathing, according to the bungalow's owner.

He told Aftonbladet that he was alerted to the tragedy by resort staff who heard the commotion. The surviving couple, who shared the twin room, heard a scream and investigated, finding their friends on the floor.

The man, the bungalow owner said, was alive when placed in an ambulance but died before reaching a local hospital. The owner said electrocution could not have been the cause because another person was also showering in an adjacent room at the same time, using water from the same source.

The investigating officer told Phuketwan today that the results of the initial autopsy could take up to 15 days to reach police. A second autopsy may be undertaken in Sweden at the behest of Swedish police or the families of the victims.

A woman who answered a call to the Krabi bungalow today said she was a new employee and knew nothing about the deaths on April 2.

Aftonbladet reported that Robert Karlsson Svard, 34, from Stockholm, died of electrocution in a shower in his hotel room in the Phuket resort of Patong in 2007.

Two young female tourists - American Jill St Onge and Norwegian Julie Bergheim - died from a still undetermined cause after falling ill at the Laleena Guesthouse on the Krabi island of Phi Phi in May, 2009.

A second autopsy on Miss Bergheim by forensic pathologists in Norway failed to produce a reason for the deaths.