Thai authorities are continuing to investigate after two Canadian women were found dead in a hotel room at a popular resort island in southern Thailand.

The women do not appear to have been murdered and their belongings were not taken, according to Thai police.

Police are working to determine the cause of death for the sisters, Noemi Belanger, 26, and Audrey Belanger, 20.

Their bodies were discovered Friday in their room at the Phi Phi Palm Residence Hotel on Phi Phi Island.

When they were located there were signs of vomit and blood on the women’s faces, which police said could have been signs of a toxic reaction.

There were no sign of fighting or robbery, but police did locate several kinds of over-the-counter drugs.

The most important evidence will be an analysis of the contents of the victims’ stomachs, according to police.

Hotel staff told officials the pair went out Tuesday night but stayed in their room all day Wednesday. By Friday hotel staff had become concerned and went into the room to check.

Police said it’s believed the women had died nearly 24 hours before their bodies were found.