Six people who died in a luxury hotel suite in Thailand were poisoned by drinks laced with cyanide, police said.
Police suspect that one of the victims was behind the poisoning and that it was motivated by overwhelming debt.
The six deceased were found dead by housekeepers at the Grand Hyatt Erawan hotel in the Thai capital Bangkok on Tuesday evening.
Investigators believe they had been dead for 24 hours.
Two of the six people had lent “tens of millions of Thai baht” to another deceased person for investment purposes, authorities said. Ten million baht is worth nearly $280,000 (£215,000).
The discovery of the bodies had caused some mystery. Initial local rumors suggested a shooting. The police later denied this information.
A clearer picture of what might have happened is now emerging.
At a news conference on Wednesday, Bangkok Deputy Police Chief Gen. Nopassin Poonsawat said the group had checked into the hotel separately over the weekend and had been allocated five rooms – four on the seventh floor and one on the fifth.
They were supposed to leave on Monday but didn’t.
Four of the victims are Vietnamese nationals Thi Nguyen Phuong, 46, her husband Hong Pham Thanh, 49, Thi Nguyen Phuong Lan, 47, and Dinh Tran Phu, 37.
The other two are U.S. citizens: Sherine Chong, 56, and Dang Hung Van, 55.
On Monday afternoon, all six of them had gathered in the room on the fifth floor.
The group ordered food and tea, which were delivered to the room at around 2pm local time (8am BST) and received by Ms Chong – who was the only person in the room at the time.
According to the deputy police chief, a waiter offered to make tea for the guests, but Ms. Chong declined. The waiter said she “spoke very little and was visibly stressed,” authorities said.
The waiter then left the room.
The rest of the group then began to stream into the room at various times between 2:03 p.m. and 2:17 p.m. No one else appears to have entered the room, other than the six people inside.
Police say there were no signs of struggle, robbery or forced entry.
They then found traces of cyanide in all six cups of tea.
Footage released by police shows untouched plates of food left on a table in the room, some of them still covered in plastic wrap.
The group’s hotel reservation included a seventh name, that of the younger sister of one of the victims, who had left Thailand last week for the Vietnamese coastal city of Da Nang and is not involved in the incident, police said.
Relatives questioned by police said that Thi Nguyen Phuong and Hong Pham Thanh, a couple, owned a road construction company and had given Ms Chong money to invest in a hospital construction project in Japan.
Police suspect that Mr Tran, a makeup artist based in Da Nang, was also “duped” into making an investment.
Mr Tran’s mother, Tuy, told BBC Vietnamese that her son had left for Thailand on Friday and called home on Sunday to say he had to extend his stay until Monday. That was the last time his family heard from him. She called him again on Monday, but he did not answer the call.
Ms Chong hired Mr Tran as her personal makeup artist for the trip, one of her students told BBC Vietnamese. Mr Tran’s father, Phu, told Vietnamese media that his son was hired by a Vietnamese woman last week to travel to Thailand.
The US FBI is assisting Thai authorities in their investigation, Thai Prime Minister Srettha Thavisin said.
Additional reporting by BBC Thai and Thuong Le of BBC Vietnamese
