The unidentified woman, 43, worked for a local election committee from 6:30 to 9:30 a.m. on Sunday, the Bac Tu Liem District People's Committee said Monday.
"The woman was not part of the election committee and only supported from the outside," said the People's Committee, adding that contact tracing efforts are ongoing, with over 200 people having had their samples taken for Covid-19 testing.
Four buildings of Goldmark City with more than 1,900 apartments that house over 5,700 people have been isolated. Authorities are also re-routing traffic near the area, and disinfection is underway.
Goldmark City on Ho Tung Mau Street of Bac Tu Liem has nine buildings with nearly 5,000 apartments. Many of its residents are South Koreans.
The woman made contact with another confirmed coronavirus case on May 20, who is her coworker. She talked with the infected coworker for about a minute while wearing a mask and staying two meters apart, according to the Bac Tu Liem medical center.
Further tests are required before she could be confirmed a Covid patient.
The national election to choose National Assembly and People's Council members of all levels for the 2021-2026 term was held on Sunday. In Hanoi, over 5.4 million voters went to over 4,800 polling stations to vote.
The city has recorded 110 Covid-19 local cases so far in the nation's latest coronavirus wave.