Dam said told at an online meeting Saturday that this was "a very important task" in the coming days and called for all forces of the Ministry of Health, the Hanoi municipality and the Bach Mai Hospital to carry out the mission. "The elimination of Covid-19 outbreaks is crucial when it has spread to the community."

Vietnam "has done a good job" with outbreaks in Son Loi Commune in northern Vinh Phuc Province with seven confirmed cases, central Binh Thuan Province with nine cases and the Vietnam Airlines flight VN54 that landed March 2 in Hanoi, getting at least 16 people infected.

However, there are still two virus epicenters in the country – the Buddha Bar in Saigon’s District 2 with 13 confirmed cases and the Bach Mai Hospital with 16, including the latest four confirmed early Sunday morning.

Dam asked for a list to be made of all people who’d been to the hospital since March 12. All localities whose residents had been to the hospital must take stronger measures and cooperate with relevant agencies to stamp out the Covid-19 outbreak completely, he said.

Deputy Minister of Health Nguyen Truong Son said Bach Mai Hospital was "a big, dangerous outbreak." He said the ministry has set up a special task force to carry out epidemiological investigations.

Hanoi Chairman Nguyen Duc Chung had said at a meeting Wednesday that the Bach Mai Hospital was at high risk of becoming a new Covid-19 outbreak center like the Daegu Hospital in South Korea, given common factors like a heavy patient load and large crowds.

The hospital has suspended admission of new patients and been isolated since Saturday morning. Nearly 5,000 staff and patients at Bach Mai had been ordered to take Covid-19 tests by this Sunday.

Son said that the hospital is a large medical facility that sees 10,000-15,000 passers-by every day, so the infection can spread not only from patients and medical workers, but also from visitors. Therefore, the risk of infection in Bach Mai as well as other hospitals is enormous, he noted.

Officers and medical staff quarantined at the Bach Mai Hospital continue to treat patients still stuck inside. The Health Ministry will provide medicines, equipment and other medical supplies and to ensure that the staff can provide complete treatment for patients, Son added.

Associate Professor Tran Dac Phu, former director of the Health Ministry's Preventive Medicine Department, said that over the past two weeks, epidemiologists have been closely monitoring and analyzing day and night to find out the infection route at the Bach Mai Hospital.

Initially, experts focused on the direction of infection from medical staff, but after testing, it was not convincing enough. The second route of transmission was signs of infection from patients and patients' relatives.

However, subsequent epidemiological investigations showed that the source of further danger was from employees of companies providing catering and logistics services for the hospital. Currently, seven people of Truong Sinh Company, which provides food and hot water to Bach Mai Hospital, have been confirmed infected with the virus.

Epidemiologists are continuing to investigate the source of infection from professional patient caregivers as well.

Phu said that the risk of infection from these two above sources "is very dangerous because they move through many hospitals."

On Saturday night, the Vietnamese Army's Chemical Division disinfected the entire area of Bach Mai Hospital.

Of Vietnam's 179 confirmed Covid-19 cases so far, 21 have been discharged after treatment, including three in Da Nang Friday and a British man in Hue on Saturday morning.

Many of the currently active cases are Vietnamese nationals returning from Europe and the U.S. and foreigners coming from the same regions.

The Covid-19 pandemic has killed more than 30,000 people in 199 countries and territories.