SINGAPORE: Singapore's manpower ministry said authorities were investigating the possibility of COVID-19 re-infections among residents in a migrant workers' dormitory, after finding about a dozen positive cases in the facility.

Hundreds of residents from the dormitory will be sent to a government quarantine facility, local media reported.

Authorities had conducted COVID-19 tests on all residents at Westlite Woodlands Dormitory after a 35-year-old worker was found positive on April 20 as part of routine testing.

The worker had completed his second vaccination dose on April 13. His room-mate also tested positive.

To date, at least 10 recovered workers were found to be COVID-19 positive.

"These cases were immediately isolated and conveyed to the National Centre for Infectious Diseases (NCID) to investigate for possible re-infection," the manpower ministry said in a statement issued on Wednesday.

The more than 1,100 residents from the block where the cases were found will be sent to a government quarantine facility for 14 days, Channel NewsAsia reported on its website, citing a letter from the dormitory operator.

The manpower ministry and the operator did not immediately respond to a request for comment.

Singapore last reported more than 10 cases in a single day among dormitory residents in September, with barely any new infections over the last few months.

The city-state has largely brought the virus under control locally and has been rolling out vaccinations.

The health ministry has previously said the vaccines were effective in preventing symptomatic disease but further research was required to determine if they will also prevent onward transmission.

The bulk of the more than 60,000 COVID-19 cases since the pandemic started, occurred in the cramped dormitories that house mainly South Asian low-wage workers, triggering lockdowns of the facilities.

The workers in the dormitories are still mostly separated from the rest of the population in the city-state, typically only allowed out of their residence for work.

Separately, Bloomberg News reported, citing sources, that Singapore and Hong Kong had called off an announcement planned for Thursday on an air travel bubble between the two financial hubs.