A woman and her ten-year-old son suffocated to death after a fire broke out in the 18-storied JSC building in Hanoi's Thanh Xuan District on Wednesday.
Witnesses said the fire started from the building's garbage storage room at around 6 p.m. and smoke then spread to the upper floors through a pipe that families shared to dump their trash.
Smoke was especially thick on the two top floors and because the lifts were suspended, hundreds of residents, mostly the elderly and children, were frightened and hysterical, they said.
Firefighters had to use ladders to bring them down and it took them an hour and a half to put out the fire.
To Xuan Thieu, head of Hanoi's Fire Prevention and Fighting Agency, told newswire VnExpress that 44 people, including two foreigners, were rushed to local hospitals.
Vuong Lan Phuong, 43, and her son Luu Gia Minh died later the same day.
Nguyen Canh Kien, who discovered the fire, said: "It's very likely that the fire had been burning for a long time [before being detected], as I was literally choked with smoke when I opened the flap."
Thanh Xuan District police launched an investigation into the case.
Thieu said it was likely that somebody put ash or coal in their trash bags before throwing it into the garbage room.
Officials said this was the second fire that had started in a building's garbage storing facility in Hanoi. The first one was recorded last June at a 13-storied building.
According to the firefighting agency, the JSC 34 building, which has 180 apartments, did not have an automatic firefighting system.