Two more pre-school staff have been diagnosed with Covid-19, as new cases in the community edged up to 11.

The Ministry of Health (MOH) said in its daily update yesterday that both the employees had gone to work after their swab test. They are a 54-year-old Singaporean woman who worked at Shaws Preschool in Lorong Chuan, and a 24-year-old Filipino who worked at the PCF Sparkletots @ Gambas.

They are among 642 new cases reported in Singapore yesterday, which brings the country's total to 31,068. Foreign workers living in dormitories continue to form the bulk of new cases.

Pre-school staff are being actively screened for the virus ahead of the centres reopening on June 2, and the two newly confirmed cases are among the seven pre-school staff who have tested positive for the infection, said the Early Childhood Development Agency in a statement last night.

About 15,300, or more than 99 per cent of all pre-school staff who had undergone testing so far, have tested negative, added the agency.

Another newly confirmed case is a 20-year-old Singaporean man who worked at 31 Sungei Kadut Avenue and Cochrane Lodge I, which are both worker dormitories that have been gazetted as isolation areas. He had worked at the dormitories after the onset of his symptoms on May 16.

Aside from another unlinked case and the two pre-school employees, the rest of the 11 cases in the community are linked to existing clusters or cases.

Two new clusters have also been discovered, said MOH.

Five earlier confirmed cases were found to be linked to a new cluster at 28 Kian Teck Road, and another 15 confirmed cases formed a new cluster at 121 Tuas View Walk 1.

The number of unlinked cases in the community has increased to an average of two per day in the past week, up from an average of one case a day two weeks ago.

The average number of new daily community cases - which does not include foreign workers staying in dormitories - has also risen from five cases two weeks ago to seven in the past week, said MOH.

The ministry said this is partly due to active surveillance and screening of nursing home residents and pre-school staff, resulting in more cases being picked up in the past week.

But more have recovered, and another 927 Covid-19 patients have been discharged. This means that about 45 per cent of all Covid-19 patients in Singapore have fully recovered.

Of the 711 patients in hospital, eight are in intensive care.

To date, close to 9 per cent, or 28,806, of the 323,000 migrant workers staying in dormitories have tested positive for Covid-19.

Twenty-three patients have died from Covid-19 complications here and nine who tested positive have died from other causes.