At around 4 p.m. Nguyen Duy Ky, 38, a scrap vendor in the central province’s Quynh Luu District, brought the cylinder to the automobile garage owned by Le Tien Hien, 28.
Ky wanted it cut open with a welding torch.
Hien asked his employee, Nguyen Duy Nhat, 30, to help him with the task.
As the two cut the cylinder, it suddenly exploded.
Locals rushed to the place after hearing the blast.
They were too late to save Hien but took Nhat, Ky and the three children aged eight to 14 who were playing nearby, all seriously injured, to the district hospital.
Nhat died in hospital while the other victims were transfered to bigger hospital.
Ky had his right leg amputated at the Nghe An Hospital for Orthopedics and Traumatology.
One of the children, Ho Khanh Vy, 8, had her right arm amputated and has been put on a ventilator at Nghe An Maternity and Pediatrics Hospital.
District authorities said the cylinder might be a compressed oxygen tank.
Police have cordoned off the garage for investigation.