The PAP Community Foundation (PCF) is reviewing its operations with staff, as another teacher at its Fengshan PCF Sparkletots centre in Bedok North and a family member of its principal tested positive for the coronavirus.
There are now 20 cases linked to Singapore's newest Covid-19 cluster - 15 staff and five family members.
Five children who had said they felt unwell have tested negative for the virus, Minister for Social and Family Development Desmond Lee told reporters yesterday.
The 10 other staff and about 110 pupils from the Fengshan pre-school at Block 126 are now under quarantine. Another 30 PCF staff from other centres are also under quarantine as they had attended training with the Fengshan PCF centre's principal.
The country's largest pre-school operator will "take a pause" and has closed all the 360 centres it runs for four days from yesterday to revisit with staff its standard operating procedures and guidelines, said Mr Lee. This will be done to reassure parents that PCF "will continue to provide and strengthen protocols in place for pre-schools".
He said: "Some may perceive that in this particular case, some teachers who were not well ought to have left the centre immediately, rather than carry on with their duties for a couple more hours.
"But I hope that parents, the public and other colleagues recognise the realities on the ground, and not in a two-dimensional way. Because I am sure the teachers concerned, the operators, managers, in hindsight, have seen facts and they will take the necessary measures hereafter... in order to hold to account the causes for what happened."
He added: "I think we should not jump to any conclusions to say any one teacher or principal had been the entry point for this Covid-19. Let's have a heart for the feelings of the teachers concerned.
"There is no indication at all as to whether they were complacent or (had) broken the rules... they were quite zealous in making sure that children were cared for. But perhaps (there were) some moments lost, a couple of minutes, hours.
"Nevertheless, this is not the time for us to pin and assign blame."
Fengshan MP Cheryl Chan said the town council has stepped up cleaning of common areas near Block 126 and throughout the estate.
"It is understandable that parents are concerned about the situation," she said, adding that PCF staff are monitoring the health of the centre's children through phone calls.
Giving an overall update, Mr Lee said that so far, three children of pre-school age have tested positive for Covid-19. In total, 320 pre-school children have been given leave of absence as they live with a person who has been put under quarantine.
Another 4,500 children and 1,200 staff in pre-schools have been issued leave of absence after returning from overseas from March 14.
Another 438 pre-school children and 170 staff have been issued stay-home notices, based on their travel history to any country.
Mr Lee acknowledged that some parents prefer to keep their children at home during this period despite stepped-up measures in pre-schools since January.
He said: "We, as a sector, need to maintain the measures that are needed at this time, and to uphold them to the highest standards.
"Operators all know that we owe it to the parents so they have peace of mind. We also owe it to all the teachers because they continue to come to work, knowing that they have a duty and a responsibility."