A Vietnamese American, Sherine Chong, has been identified by Thai police as the suspect who is believed to have poisoned five others at the luxurious Grand Hyatt Erawan hotel in Bangkok, before killing herself with the poison.

Cyanide poisoning is likely the cause of the deaths, police said.

Chulalongkorn Hospital said on July 17 that an autopsy of the six people found dead in a hotel suite found traces of cyanide.

The bodies showed traces of the rapid-acting chemical and had purple lips, indicating a lack of oxygen, the hospital’s Dr Kornkiat Vongpaisarnsin told reporters, adding that more tests were being conducted.

Thai investigators concluded that Chong was culpable after questioning witnesses, including the daughter of one of the dead, said Police Major-General Theeradej Thumsuthee, the head of investigation at Bangkok’s Metropolitan Police Bureau, according to Thai newspapers Khaosod and Bangkok Post on July 17.

Debt issues may be the motive behind the deaths, said Maj-Gen Theeradej. Thai police are not considering other possible suspects, as Suite 502, where the bodies were discovered, had been locked from the inside and no one else was found to have entered. There were no signs of a struggle.

Chong is suspected to have poisoned the others before killing herself, Thai police said on July 17, adding that they are looking for the source of the cyanide.

“The case likely stems from a debt problem,” Maj-Gen Theeradej said. “There are no other possibilities. The culprit is among the six (dead) because they were the only people who entered the room. There were no others.”

The debt may be the result of a construction deal that went south.

Investigators believe the victims had been dead for 24 hours by the time they were found.

After questioning witnesses, including some of the dead people’s relatives, investigators said the victims were a mix of borrowers, lenders and guarantors. Two of the dead were married to each other and owned a construction business.

Bangkok deputy police chief Noppasin Punsawat said witnesses told the police Chong had been given the equivalent of around 10 million baht (S$373,000) by the couple to build a hospital in Japan.

The couple, aged 49 and 47, had suspected her of cheating them as there had not been much progress in the project and arranged to meet to iron out their differences in Thailand after visa issues prevented them from meeting in Japan.

The three men and three women who were found dead were of Vietnamese descent. Two of them – including Chong, 56 – were American citizens.

One of the victims was 37-year-old make-up artist Phu Gia Gia, who reportedly worked with Vietnamese celebrities and beauty queens. He was mourned by his family, as well as his fans, who left condolence messages on his Facebook page when news broke of his death.

He was said to have been persuaded to invest in the project.

Their bodies were found by hotel staff in a fifth-floor room of the Grand Hyatt Erawan around 5.30pm on July 16, hours after they had been expected to check out.

Their belongings, which had been packed as though the victims were ready to leave, have been taken by the police for investigations.

Closed-circuit television footage captured all six entering the hotel with their suitcases on the afternoon of July 15, likely making their way to the suite. It is likely the last time they were seen outside the room.

The group had booked several rooms under seven names on different floors, said Bangkok police chief Thiti Saengsawang.

The seventh person is the younger sister of one of the dead, the Khaosod news outlet reported. She had left Thailand on July 10 and is not suspected to have been involved in the deaths.

Lieutenant-General Thiti noted that the group of six had ordered food via the hotel’s room service, but it was untouched, and only some drinks were consumed. Photos of plates of fried rice, vegetables and tom yum soup wrapped in plastic have been circulating online. Only one of the plates had its plastic seal removed.

Forensic investigators said they found cyanide in a thermos flask, teapot and six cups in the room, reported Khaosod on July 17. The officers described cyanide as a toxic, potent substance that is tasteless and odourless, so the guests would not have been able to tell that it was in their drinks.

The cyanide had been mixed into a pot of tea suspected to have been brewed by Chong. Showing a darkened teabag taken from the scene, forensic investigators said the tea was abnormally dark, leading them to suspect that it was laced with a large amount of toxic substances.

A hotel employee had delivered the food and drinks to Suite 502 when Chong was alone in the room, Khaosod reported. Chong also turned down an offer by the worker to make tea, saying she would do it herself.

The server had told the police that Chong appeared stressed.

“We found cyanide in the teacups; all six cups we found cyanide,” commander of the Thai police evidence office Trirong Phiwpan told a press conference on July 17.

He added that cyanide blocks blood cells in the body from taking in oxygen, and the poison would take effect in less than five minutes, depending on the amount consumed.

Police investigations are ongoing. The US Federal Bureau of Investigation is assisting in the investigation. Vietnam’s embassy in Bangkok said it was working with the Thai authorities on the case.

Thai Prime Minister Srettha Thavisin on July 16 ordered a swift probe into the case to limit any impact on the kingdom’s tourism sector.

The Grand Hyatt Erawan hotel in downtown Bangkok is a five-star luxury hotel popular with tourists. It is next to the Erawan Shrine, which regularly attracts throngs of devotees.

Asia News Network (ANN)/The Straits Times