People walk outside a hotel where a number of people were found dead in Bangkok, Thailand, on Tuesday. AP

Six people believed to be Vietnamese and Vietnamese-Americans were found dead in a hotel room in central Bangkok on Tuesday, a senior police officer said

"Hotel staff found their bodies in a room around 5:00 pm (1000 GMT) today," the officer said, speaking on condition of anonymity.

He denied initial reports that the six had been killed in a shooting, saying the investigation was currently focused on a "link with a toxic substance."

Some of the six foreigners appeared to be on their first trip to the country, while others appeared to be return visitors, he added.

In a statement, the police said they were still investigating the scene and cause of death.

There was no immediate official confirmation of which hotel was involved, but police and investigators were seen outside the Grand Hyatt Erawan in the upscale Ratchaprasong district.

Prime Minister Srettha Thavisin arrived on the scene shortly after 9:00 pm.

Agence France-Presse