King Restaurant on Le Lai Street in District 1 was found operating six karaoke rooms with dozens of customers inside on Tuesday night by a team of inspectors headed by city vice chairman Duong Anh Duc.
"The delegation was on patrol without notifying local authorities," Duc said.
The police have not announced the fine yet, but said the restaurant could be punished for "failing to suspend business activities or services in public places to contain Covid-19," which carries a cash penalty of VND20-40 million ($867-1,730).
The customers included eight Chinese and Japanese men who were inside with several female restaurant staff.
One of the Chinese men had just completed his 14-day mandatory quarantine on entering Vietnam and was still in the self-quarantine period. Protocol requires him to isolate himself at his place of accommodation for a week, avoid crowded places and keep a distance from people at the workplace.
Medical personnel were dispatched to the restaurant to take samples from around 50 staff and customers to test for Covid.
Since April 30 all bars, discotheques and karaoke parlors in the city have been closed.
A day earlier a man in Binh Tan District was diagnosed with the disease. Until then the city had gone 75 days without local transmission.
The man from the northern province of Ha Nam was visiting relatives in the city when he tested positive. He had come into contact with a man who had returned from Japan and was later found to be infected.
As of Wednesday Vietnam had 38 Covid patients in the ongoing outbreak that began on April 27 after more than a month’s hiatus.
Of the 38, 35 are linked to hotspots in the northern provinces of Vinh Phuc and Ha Nam, where people have been found to have Covid after completing the mandatory 14-day quarantine and testing negative two or three times, including the Japan returnee.