The Ministry of Health (MOH) confirmed 573 new coronavirus cases in Singapore as of noon yesterday, 98 per cent of whom were migrant workers in dormitories.

Three new clusters were identified. These are at Hai Leck Engineering at 9 Tuas Avenue 1, Melody Springs construction site at 477A Yishun Street 44 and another new cluster at 6 Tuas Basin Link.

Meanwhile, the ministry has closed two clusters - Little Gems pre-school and the dormitory at 55 Sungei Kadut Loop, as no more new cases were linked to them in the past 28 days, or two incubation periods.

Yesterday was the 11th day in a row with daily cases below 1,000. The new cases bring the total number to 18,778.

Work permit holders residing in dormitories make up 560 of the new cases. The ministry said the number of migrant worker cases remains high owing to the extensive testing in these premises.

To date, 16,393 - or just over 5 per cent - of the 323,000 foreign workers in dorms have tested positive.

New local cases outside dormitories comprise five Singaporeans and permanent residents, and eight work permit holders.

There were no imported cases.

Singapore also saw three new cases from the public healthcare sector. One of them is a 52-year-old Singaporean working at the Singapore Expo community care facility as a healthcare volunteer, said MOH.

She was confirmed to have Covid-19 yesterday and is warded at the National Centre for Infectious Diseases (NCID).

Another is a 32-year-old Singaporean who worked for a few hours as a doctor at Changi General Hospital (CGH) before she was admitted. She is warded at CGH.

The third case is a 33-year-old Singaporean who worked as a facilities manager at NCID. She is warded at Tan Tock Seng Hospital.

All three did not travel recently to countries or regions affected by the coronavirus.

MOH said 49 more cases have been discharged from hospitals or community isolation facilities, bringing the total number of those who have fully recovered to 1,457.

There are 1,491 confirmed cases still in hospital, with 25 in critical condition in the intensive care unit. Community isolation facilities have another 15,812 cases.

Of the new cases, 89 per cent are linked to known clusters, while the rest are pending contact tracing.

New local cases, excluding those in dormitories and other work permit holders, have dropped to an average of nine a day in the past week, from 20 the week before.

The average daily number of such unlinked cases has also fallen to four from 12, in the same period.

In the past week, from April 27 to May 3, MOH has uncovered links for 798 previously unlinked cases.

Yesterday, Health Minister Gan Kim Yong said Singapore could consider easing further the strict circuit breaker measures if the virus situation improves by June 1.

For it to happen, community cases would have to remain low or drop further, while cases in migrant worker dormitories would need to come "clearly under control".

The country will also need to drastically ramp up its capacity to test for the virus before the economy can restart, he said, adding that there are plans to increase testing capacity to 40,000 tests a day, up from the current 8,000.