Traces of Cyanide Found in Bangkok Hotel Room Where Six Died

The Thai police said on Wednesday that they had found traces of cyanide on flasks and tea cups in a Bangkok hotel room where six bodies were found the previous day, and that one of the people found dead was believed to have administered the poison.

Maj. Gen. Noppasin Poonsawat, the deputy police chief in Bangkok, told reporters that one of the six people “did this by using cyanide.” He did not identify the person. General Noppasin said the group had gathered in Bangkok to discuss an investment plan in which several of them were involved.

The bodies were found on Tuesday in a hotel room at the Grand Hyatt Erawan in the heart of downtown Bangkok, and little was immediately revealed about how they had died. The case has shocked Thailand, and officials have rushed to offer assurances that the country, one of the world’s most popular tourist destinations, remains safe.

The police identified the dead as Sherine Chong and Dang Hung Van, both Vietnamese Americans, and Nguyen Thi Phuong Lan, Pham Hong Thanh, Tran Dinh Phu, and Nguyen Thi Phuong, all Vietnamese citizens.

Ms. Chong and Ms. Lan were brokers in an investment plan, General Noppasin said. Ms. Phuong and her husband, Mr. Hong, had given Ms. Chong 10 million baht, or nearly $280,000, and were asking for updates on their investment, he added. They had agreed to discuss the issue in Japan, but they met in Bangkok instead because of visa problems, the general said.

On Monday, the group gathered in Ms. Chong’s room, according to the general’s account. The others had checked out of the hotel and brought their bags to Ms. Chong’s room. They ordered room service, including two thermoses of hot tea.

A hotel employee who entered the room at 1:51 p.m. only saw one woman, who took the food and drinks, the general said. He said the employee offered to make the tea, but the woman refused and said she would make it herself.

The bodies were found roughly 24 hours later. On Tuesday night, police officials said initially that the victims had been poisoned, but later walked back that claim. At the time, they said they were looking into a seventh person who was booked at the hotel, but on Wednesday, General Noppasin said they had ruled the person out.

Mr. Phu was a well-known makeup artist who had worked with many Vietnamese celebrities. He had traveled to Thailand to help a bride get ready for her wedding about 10 days ago, according to a report in Nguoi Lao Dong newspaper, a Vietnamese newspaper, which cited Mr. Phu’s relatives. His family said they did not know whom he traveled with and that he was often on the road, according to the newspaper.

His father, Tran Dinh Dung, 65, told the newspaper that his wife had fainted numerous times since learning of her son’s death.

“She could not bear the shock,” Mr. Dung was quoted as saying.