Twenty-four people who took part in a religious gathering in Delhi’s Nizamuddin area have tested positive for the coronavirus disease (Covid-19), state health minister Satyendar Jain said on Tuesday, while health officials scrambled to trace the footprints of other attendees who have spread out across the country amid fears of a possible explosion of the infection.

An estimated 1,500-1,700 people, including 227 foreigners, are believed to have attended the annual gathering at the six-storey hostel-like headquarters of Tablighi Jamaat, a Muslim sect, earlier this month, according to Jain.

He said 700 people who attended the congregation were quarantined while around 335 admitted to hospitals after showing signs of the fast-spreading infection caused by the Sars-CoV-2 virus.

A senior bureaucrat in southeast Delhi, where the building is located, said officials will locate, identify and facilitate the quarantine of all Indian citizens who attended the event, hinting at a massive and challenging exercise that will have to cover several states.

“The gathering size was more than 1,500, which include more than 200 foreign nationals…This is the biggest local coronavirus operation in Delhi. We have to first draw out a list of people. We are on it,” the bureaucrat who spoke on the condition of anonymity.

Jain said organisers of the gathering flouted Delhi government’s orders issued to stop the spread of Covid-19.

“ The organisers have committed a grave crime. I have written a letter to LG (lieutenant governor) Anil Baijal to take strictest action against the organisers. We have given directions to the police to lodge and FIR as well,” Jain said, a day after the Delhi government ordered the filing of the first information report.

The state banned on March 13 any seminar or conferences having more than 200 people in the city. Three days later, it prohibited any form of religious, academic, political, social, cultural, personal gathering involving over 50 people.