Update at 2.25pm:
The kindergarten involved has provided more details regarding the incident.
According to The Straits Times, a teacher who carried out daily health checks on the children on the morning of Feb 14 had first found bruises below the girl's eye.
Ms Kwan explained this was caused by an accident at home involving her son, said the school.
About two hours later, another teacher noticed a bruise on the girl's ear.
However, the child similarly claimed she had been accidentally hurt by her brother at home.
As this was consistent with Ms Kwan's explanation of the earlier bruises, the school did not take immediate action to inform her about the girl's bruised ear, added the school in its statement.
Ms Kwan was informed in a phone call on the same day that her daughter had "behaved normally in school" and they were unaware of any incident that could have caused the bruises on her ear.
The school said: "We have been extending our fullest cooperation on its investigations.
"We also note that she returned to kindergarten on the next day and enjoyed the Chinese New Year celebrations with her friends."
Having carried out its own investigations by reviewing closed-circuit television footage and interviewing staff members, the school "did not find any incident or circumstances that could have caused those injuries in the kindergarten".
Police are investigating a report lodged by a mother whose young daughter was found with a bruised and swollen ear after the latter returned home from her pre-school on Feb 14.
Ms Kwan said in her post that she sent her three-year-old daughter, who was "perfectly normal and happy", to school on the morning of Feb 14.
However, when her husband picked up their daughter from school later that day, "he sensed that something was not right" with the child's mood.
Ms Kwan wrote: "Her messy hair covered part of the ear and she was sweaty after a whole day in school but what he saw was a horrific bruise on the top of her ear.
"When they reached home, my hubby asked me to check what had happened to her ear and to my horror, her ear was badly bruised to such an extent that it was swelling badly.
"My heart bled and when I asked my daughter about what had happened, she lost control and just broke down into tears and cried."
According to Ms Kwan, who also shared photos of her daughter's injury, none of the teachers at the pre-school could explain what caused the bruise.
She said she took her daughter to a paediatrician, who was "shocked" by the injury and "diagnosed it as a form of traumatic bruising that was caused by the exertion of great intentional force, and not a result of insect bites or drug allergies".
A visit was made to another paediatrician at KK Women's and Children's Hospital (KKH) on Feb 15 and the bruise was classified as a "non-accidental injury", added Ms Kwan.
The mother, who said she has reported the incident to the police, Early Childhood Development Agency (ECDA) and a Member of Parliament (MP), also shared how her daughter has been "traumatised badly".
"She is tormented day after day by the incident and her behaviour has even undergone drastic changes. She is now very temperamental and bursts into rage or tears at times, sometimes even out of the blue for no apparent reason," wrote Ms Kwan in her post.
She added that her daughter, who has stopped attending the pre-school, also suffers nightmares every night for the past three weeks.
In response to a query by Stomp, the police confirmed that a report was lodged and investigations are ongoing.
"The investigation officer has updated Ms Claudia Kwan on the status," said the police.
In a statement, the ECDA told Stomp that it is aware of the case and has reached out to Ms Kwan to provide any necessary assistance that she and her child may require.
It added: "At the same time, ECDA is working with the centre to ensure the safety and well-being of the children at the centre."