The two patients living in Tien Tien commune of Phu Cu district had tested positive for the virus twice, said a leader of the provincial Department of Health.
They were said to travel to Ha Nam province to visit their relatives. During their stay, they met a local resident who was later confirmed as a coronavirus infection case.
Both patients were immediately transferred to Hanoi-based Hospital for Tropical Diseases for medical observation and treatment following their positive tests.
Hung Yen health officials hosted an urgent meeting with Phu Cu district authorities to deploy anti-coronavirus measures.
Local authorities initially identified 16 people who had come into close contact with the two patients.
The Ha Nam case is a 28-year-old man returning from Japan on April 7. He tested positive for the SARS-CoV-2 virus after completing a 14-day quarantine period according to COVID-19 rules on April 22.
Notably, four of his relatives living in the same house were also infected with the virus.