Singapore is investigating 13 cases of COVID-19 infections among people who served their quarantine at a hotel along the city’s Orchard Road shopping strip.

The cases, all imported, had “high genetic similarity” despite the victims arriving from 10 different countries, the government said in a statement on Saturday. Singapore said it conducts whole genome sequencing and phylogenetic analysis on all COVID-19 cases, and it takes about four weeks to culture the virus and complete the sequencing.

The people were confirmed between Nov. 2–11 to have COVID-19, and had stayed at the Mandarin Orchard Singapore hotel between Oct. 22 and Nov. 11. They arrived from places including Bahrain, Canada, Indonesia, Myanmar, Netherlands, the Philippines, South Korea, the UAE, the UK, and the US.

“Epidemiological investigations were immediately initiated to determine if there is a potential link between these 13 cases, and to study if transmission could have occurred locally, and not from their country of origin,” according to the statement. From “preliminary investigations, we cannot exclude that transmissions could have occurred at Mandarin Orchard Singapore.”

Authorities are conducting analysis on more cases beyond Nov. 11. The hotel had stopped taking visitors for quarantine purposes since Dec. 13. Those currently serving their so-called stay-home notice will be sent to another facility, the government said.

The Mandarin Orchard is one of the hotels approved by authorities to offer staycation packages to Singapore residents eager for a break and unable to leave the country because of travel restrictions. While those on quarantine are housed on dedicated floors and segregated from other guests, the hotel will check out all occupants as a precautionary measure, and close all restaurants and event spaces.

The health ministry is also testing about 500 employees of the hotel for COVID-19.

For the past two months, the number of infections in the community has been at or near zero in the city-state of 5.7 million people. — Wes Goodman/Bloomberg