Two men and a woman had been quarantined for 14 days at a military facility in Chi Linh Town, Hai Duong Province as soon as they returned from Russia on August 10.

All three had been tested for the novel coronavirus once and the results were negative.

On Tuesday morning, they left the quarantine camp and went home. However, the same afternoon, test results of their samples showed they were positive for the novel coronavirus. The tests were done by the National Institute of Hygiene and Epidemiology.

The Health Ministry confirmed the the three as patients 1032, 1033 and 1034 on Wednesday.

After leaving the camp, the three returnees met with many other people in Hanoi, the northern provinces of Hung Yen and Bac Ninh, and the central province of Quang Binh.

The Center for Disease Control and Prevention in Bac Ninh found that on his way from the quarantine camp to his home in Hanoi, the 21-year-old "Patient 1032" had stopped for pho at the Quan Son Restaurant on National Highway 18, Nghiem Xa Village, Viet Hung Commune, Que Son District at around 9:30.

The Bac Ninh CDC has identified one person at the restaurant as a first generation of contact (F1) and is calling for everyone who has visited the venue from 9:30 Tuesday to 4 p.m. Wednesday to report themselves.

Back at his home in Hanoi, "Patient 1032" had contact with his parents, brother and three friends.

Meawhile, Quang Binh health authorities said "Patient 1033," a 58-year-old woman residing in the province’s Dong Hoi Town, had left the camp in her private car and was informed about the test results during her journey home.

She returned to the camp immediately, but had stopped earlier in Hung Yen Province’s Khoai Chau District to visit some relatives. For now, two people had been identified as her F1, 22 as F2 and 58 as F3 generation contacts.

"Patient 1034," a 34-year-old resident of the northern province of Hai Duong had not met anyone after leaving camp, but has one F1, who stayed in the same room with him at the camp.

That person had also left the camp for home in An Thi District of Hung Yen Province after finishing the 14-day quarantine. So far, 14 have been identified as F2 and five as F3 contacts of "Patient 1034."

All F1 contacts of the three patients have been sent to quarantine camps in their localities and places where the patients had visited have been disinfected.

Khong Minh Tuan, deputy director of the Hanoi CDC, said as the Health Ministry has regulated, all persons returning from abroad have to be quarantined for 14 days and tested at least twice.

The first test is conducted right after entry and the second one 10-12 days later. Once they test negative for the virus twice and finish the 14-day quarantine, they would be allowed to leave.

"Even though they had completed the 14-day quarantine, the three patients had been allowed to leave the quarantine camp too early, before they had got the results for the second test," Tuan noted.

Health authorities said they are continuing to track down all contacts of the three new Covid-19 cases for quarantine and testing.

Of Vietnam’s 1,036 Covid-19 cases, 367 are active, 30 people have died and the rest have recovered.