Canadian sisters on holiday in Thailand were found dead in their hotel room covered in vomit, bleeding from the gums and displaying skin lesions several days after they checked in.The pair were discovered by chamber maids at the Palm Residence Hotel on the island of Phi Phi in the Andaman Sea after they had not answered their door for two days.Police said there were no signs of a struggle in the room and initial tests had proved inconclusive, though the condition of the women in their twenties pointed to some form of toxin being responsible for their deaths.Sisters Audrey Belanger, 20, and Noemi, 26, from Quebec, arrived at the hotel on Tuesday and went out that night, but remained in their room on Wednesday.There was no answer when staff knocked on the door on Thursday and it was only on Friday that they entered the room and found the sisters dead.Police said there was a large amount of vomit in the room and their nails had a blackened appearance, in addition to the other signs of trauma."Their bodies were found a little after midday [Friday]," said Phi Phi police Lt Pongpan Waiyawat. "We will have to wait for a post-mortem to determine the cause of death, but based on initial investigations there is no sign of violence in the room."A number of people have died in mysterious and ultimately unexplained circumstances in hotel rooms in Thailand – including Phi Phi.In 2009 an American, Jill St Onge, 27, and a Norwegian Julie Bergheim, 22, died in similar circumstances while staying at adjoining rooms at a guesthouse on Phi Phi. But in spite of pathology tests in the US and Norway the causes of their deaths were never fully established.