Laos authorities have released the names of two Danish women and one American man who died of suspected methanol poisoning after apparently drinking tainted alcohol.

Anne-Sofie Orkild Coyman, 20, Freja Vennervald Sorensen, 21, and American national James Louis Hutson, 57, were all staying at the Nana hostel in the riverside town of Vang Vieng, a travellers hub about two hours north of the capital Vientiane.

Three other tourists, including one Brit, also died from suspected methanol poisoning in the town last week.

Visiting the hostel, the Governor of Vang Vieng, Bounchan Malavong, promised an investigation and vowed to bring to justice those responsible for the deaths.

The two young Danish women were found unconscious in their hostel bedroom on November 13, after going out to a bar in the city the night before, local media reported. They were sent to a hospital in the capital Vientiane, but died in the middle of the night. The medical team said the cause of death was sudden heart failure.

On the same day the two Danes were found, hostel staff noticed that American tourist Hutson had not come out of his room. When they went in to check on him they found him lying dead on the bed, with several empty drinks glasses nearby. There were no bruises or wounds on his body, local media reported.

On a visit to the hostel, the governor pledged that those responsible for the deaths would be charged, and the hostel has been closed for investigation.

He said local authorities would make sure that local businesses were following the law.

Much of the scrutiny has fallen on the Nana Backpackers Hostel where some of the victims were staying. The Australian girls had taken free shots there before heading out for the night.

The hostel manager has denied culpability, saying the same drinks had been served to at least 100 other guests that night who reported no problems.

Methanol is a deadly substance often found in bootleg alcohol. Medical specialists say drinking as little as 25 millilitres of it can be fatal, but it is sometimes added to drinks because it is cheaper than alcohol.