Hanoi's Center for Disease Control confirmed 14 more coronavirus positive cases at the hospital Monday morning, raising the cluster tally to 23.
The facility in Hai Ba Trung District was barricaded at around 8:30 p.m. with checkpoints erected in front, and no one is allowed to enter or leave.
The military disinfected the entire hospital.
The cluster was detected after a person in Tay Ho District, who had been treated at the hospital from July 6 to July 22, was found infected on July 25.
But the exact source of the hospital outbreak has yet to be determined, Thuong said.
By 6 p.m. Sunday over 300 people were sampled for testing, he said.
Hanoi has had 903 Covid cases in the fourth wave that began in late April. Earlier too a number of infections were found in hospitals in the capital leading to lockdowns.
The city is now under a two-week social distancing order.