Traces of cyanide have been found in the tea cups of six people found dead in a luxury Bangkok hotel, police in Thailand have said.
The bodies were found on Tuesday in the Grand Hyatt Erawan hotel.
Two Vietnamese Americans and four Vietnamese nationals died – three men and three women aged 37 to 56. Initial autopsy results also showed cyanide in their blood.
Police said they believe one person poisoned the others over a bad investment.
A husband and wife among the dead had invested about 10 million baht (£200,000) with two other victims to build a hospital in Japan, according to Noppasin Punsawat, Bangkok deputy police chief.
The six had last been seen alive when food was delivered to the room on Monday afternoon.
Hotel staff saw one woman who received the food, and security footage showed the rest arriving one by one to the room shortly after.
No one was seen leaving or enterting, and the door was locked from the inside. A hotel worker found them on Tuesday afternoon when they failed to check out.
Upon entering the room, staff found the food was untouched, with some fried rice still under plastic wrap.
Several used teacups were on a nearby table, next to two thermos bottles. They contained traces of the poison.
Police said four bodies were in the living room and two in the bedroom. And two appeared to try to reach the door, but collapsed before they could.
They said a mass suicide was unlikely because some of them had arranged future parts of their trip, such as guides and drivers. The bodies being in different parts of the hotel room suggested they did not knowingly consume poison and wait for their deaths together.
Police said a seventh person whose name was part of the hotel booking was identified by police as a sibling of one of the six victims.
They left the country on July 10, and police believe they had no involvement in the deaths.
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