They began to take samples immediately after getting the orders on Wednesday night, according to the Department of Health.

The emergency move came after a patient from Hanoi's K Hospital, now a major hotspot with 13 coronavirus patients and locked down, visited the HCMC Oncology Hospital but failed to declare they had been at the Hanoi hospital.

The patient, who claimed to be a resident of nearby Binh Duong Province but is actually from Quang Tri in the central region, visited K Hospital on April 24 and the HCMC Oncology Hospital on May 12. He has tested negative for the coronavirus.

Everyone who has been to K Hospital since mid-April is required to declare this and isolate and get themselves tested for Covid.

Nguyen Tri Dung, director of the HCMC Center for Disease Control, said this was the city's first urgent mass test.

Pham Xuan Dung, director of the HCMC Oncology Hospital, said over 2,000 doctors, nurses, patients, and others who visited the hospital last week have been tested and found negative for Covid.

Nguyen Tan Binh, head of HCMC's Health Department, said the city has 24 facilities capable of testing up to 40,000 samples a day.

Duong Anh Duc, deputy chairman of the city People's Committee, said more quarantine centers need to be put up and over 10,000 beds should be available to prepare for any eventuality.

The southern metropolis has recorded only one case during the latest wave in which 644 people have been found infected in 26 cities and provinces.

But authorities have expressed concern about possible outbreaks in the city due to its proximity to the border and attempts by people to enter Vietnam illegally.