Thai Prime Minister Srettha Thavisin has ordered an investigation after six foreign nationals were found dead at a hotel in downtown Bangkok.
Police have dismissed earlier reports that they were killed following a shooting.
Metropolitan Police Bureau Commissioner Thiti Saengsawang said the bodies of three men and three women were found in a single hotel room on Tuesday and the cause of the deaths has not been confirmed, Xinhua news agency reported.
He said initial investigations suggest that the incident may have been linked to poisoning, as suspicious substances were discovered in the hotel room and no signs of struggle were found at the scene.
Prime Minister Thavisin has ordered the investigation into the incident to "prevent any impact on the public".