As many as 41 people living in a building in southwest Delhi's Kapashera area tested positive for coronavirus on Saturday, an official said.
A case of COVID-19 had been reported from the building situated in 'theke wali gali' on April 18, prompting authorities to timely seal it.
This helped in containing the spread of coronavirus in the area.
The administration will conduct tests of people residing in the building on Sunday again.
"Keeping in mind the high density of population in this particular building, the district administration took the proactive decision of sealing and containing the building on April 19," the official said.
According to the district administration, 175 samples were collected on April 20 and April 22 from the building and sent to the Nation Institute of Biologicals (NIB) in Noida.
"Out of the total samples collected from the building, reports of 67 people have come on Saturday and 41 have tested positive for COVID-19," Southwest District Magistrate Rahul Singh, who went into self-isolation after his private secretary tested positive for COVID-19, said in a video message.
The DM said tests were conducted 13 days ago and the reports got delayed due to issues of blockade at the Delhi-Noida border and backlog at NIB Noida.
As all the individuals are asymptomatic and results are 13 days old, he said, "The district administration will be conducting re-test on Sunday and to assess the present status of all positive cases."
"People residing in this building were using common toilet that's why we sealed the building and did not allow them to come out. We were waiting for their reports," Singh said.
The district magistrate said the administration contained the spread of COVID-19 in the area by sealing the building.
The guidelines mandate sealing an area where minimum three cases have been reported.
Last month, the private secretary of Singh had tested positive for COVID-19, prompting the DM to go into self-isolation.
On Friday, Delhi recorded 223 fresh cases of coronavirus, taking the tally to 3,738 with two more deaths being reported in New Delhi.
The number of fatalities due to COVID-19 now stands at 61.