Police suspect a 56-year-old Vietnamese woman with US citizenship of using a lethal mixture of cyanide and tea to poison five compatriots when they met at a hotel in Bangkok to resolve a financial dispute.

Police on Wednesday identified the suspect as Vietnam-born Sherine Chong.

Hotel staff said she had been waiting alone in room 502 on the fifth floor of the Grand Hyatt Erawan Hotel, when her alleged victims arrived on Monday.

She had earlier ordered food and tea from room service. She refused the room attendant’s offer to make the tea for her in the room, saying she would prepare it herself.

Security camera recordings showed the five other Vietnamese arriving at the room with their luggage. From 2.17pm on Monday, no one had left the room. On Tuesday evening a maid found their bodies in the room.

Chong was among them.

Police said the suspect had invited the other five people to invest in construction projects. They included a couple who reportedly invested the equivalent of 10 million baht in a hospital project in Japan. When there was no progress in the projects, they had taken legal action.

The six were due to meet in court in two weeks. Chong invited the five to meet for out-of-court negotiations.

They arrived in Bangkok at different times and stayed in different rooms at the 5-star hotel.

The five Vietnamese had checked out at noon on Monday, but Chong kept room 502 and invited them back for another round of talks. She had ordered food and tea for everyone.

Police said cyanide residue was found in the six used teacups found in the hotel room. Police were tracking down the source of the poison.