A report from the Thai Nguyen Police Department said that the fire broke out at 4 am on the ground floor of the two-storey villa on Duong Tu Minh Street in Tan Long Ward.

"Initial investigations showed that the fire started in the living room on the 100-square-metre ground floor, which was used as a store for incense sticks," the report said. "Four people who were sleeping in rooms on the ground floor managed to escape. The fire then quickly spread to the first floor, where a couple were sleeping, and they died from smoke suffocation. Their bodies were found in a bathroom on the first floor."

Some witnesses said that the couple on the first floor could not escape because the house did not have balconies or emergency exits.

"The fire spread so fast, and we couldn't access the first floor to help the couple," a neighbour said. "Firefighters arrived at 4.15 am and brought the fire under control in just five minutes. However, the house owner, Nguyen Thi Hien, and her Indian husband Alam MD Suhail had died in the debris."

Police are further investigating the cause of the fire.