Six people have been found dead in a luxury Thai hotel, and police are investigating possible poisoning as the cause.

Six people, including two Vietnamese Americans, were found dead in a luxury hotel room in central Bangkok, with Thai police investigating possible poisoning.

The bodies were discovered by staff in a fifth-floor room at the Grand Hyatt hotel after the guests missed their checkout time by over 24 hours, according to Bangkok’s Metropolitan Police commissioner, Thiti Saengsawang.

Police indicated that the incident does not appear to be a robbery, as none of the bodies showed signs of physical violence, and they do not believe the victims harmed themselves. However, cups with traces of white powder and untouched food were found in the room, leading police to consider poisoning as a potential cause.

Authorities are currently searching for a seventh person who was part of the hotel booking and is now a possible suspect.

The other four deceased are Vietnamese nationals. Police believe one member of the group tried to reach the door but collapsed before they could do so.

On Tuesday, police were seen guarding the entrance of the five-star hotel following the discovery of the bodies. The US State Department confirmed it is aware of the deaths of two US citizens in Bangkok.

“We offer our sincere condolences to the families on their loss. We are closely monitoring the situation and stand ready to provide consular assistance to those families,” said State Department spokesperson Matthew Miller during a briefing.

Miller noted that local authorities are responsible for determining the cause of death when a US citizen dies abroad and that the State Department will be in communication with Thai authorities regarding this case. He also mentioned that he did not know if the deaths were discussed during Secretary of State Antony Blinken’s call with his Thai counterpart, as the call may have occurred before the agency was informed of the deaths.

This incident follows a separate poisoning case last year, where Thai woman Sararat Rangsiwuthaporn was arrested on suspicion of murdering her friend with cyanide and charged with at least 13 counts of premeditated murder, shocking the country.