Thai police said today that traces of cyanide were found in the cups of six tourists who were poisoned at a hotel in Bangkok. The four Vietnamese and two American nationals were found dead inside a luxury room at the Grand Hyatt Erawan in Bangkok shortly before 5:30pm local time on Tuesday July 16. Lieutenant General Trairong Piwpan, chief of the Thai police force's forensic division, said there were traces of cyanide in the cups and thermoses that police found in the room, but initial results from post mortem examinations are expected Thursday. Bangkok police chief Lt. Gen. Thiti Sangsawang identified the dead as two Vietnamese Americans and four Vietnamese nationals, and said there were three men and three women. Five of the dead were named by police as females Sherine Chong, Thi Nguyen Phuong and Thi Nguyen Phuong Lan. Two dead men were Dinh Tran Phu and Hung Dang Van. The sixth has not been named. Five bodies are believed to have been inside the room and one outside the door. Police are searching for a seventh member of the group, who they suspect was involved. Police Lieutenant General Thiti Saengsang, commander of the Metropolitan Police Bureau, along with Major General Noppasin Poolsawat, deputy commander of the Metropolitan Police Bureau, were dispatched to the suspected crime scene. Police Lieutenant General Thiti Saengsang said: 'Hotel staff found the dead inside the room. They called the police immediately and forensic officers arrived. 'This was not self harm, but someone caused the deaths. We are tracing every step since they got off the plane. Thai prime minister Srettha Thavisin and other government ministers were scrambled to the hotel late on Tuesday to desperately try and protect the country's lucrative tourism industry. They assured people that it was an isolated case and ordered a swift investigation.