Mount Elizabeth Hospital has a 24-hour walk-in emergency department, but it is "not equipped or staffed to manage all forms of emergency cases", said the Ministry of Health (MOH).
This was why the six Filipino victims of Sunday's Lucky Plaza accident were not taken to Mount Elizabeth, although it was near the accident site.
The MOH added that most private hospitals "are not able to provide proper resuscitation and emergency treatment for severe and multiple trauma patients".
The ministry and the Singapore Civil Defence Force (SCDF) said in a joint statement yesterday that Tan Tock Seng Hospital (TTSH) was the nearest hospital that is equipped to handle such an emergency.
They were replying to queries on why the SCDF had taken the six Filipino domestic helpers, who were hit by a car behind Lucky Plaza on Sunday afternoon, to TTSH instead of Mount Elizabeth Hospital, which was about 200m away.
Two of the women died later from their injuries in hospital, two are warded and the other two have been discharged.
The MOH spokesman told The Straits Times that all public hospitals - except for Alexandra Hospital - have emergency departments that "can resuscitate and provide initial treatment of acute emergencies in both adults and children".
Raffles Hospital, however, is the only private hospital that meets the ministry's "minimum standards for trauma care".
But even this hospital does not have the capacity to manage "mass casualty incidents". So while ambulances have been taking patients who are not facing life-threatening conditions there since 2015, it is not a designated hospital for serious trauma cases.
Also, while most public hospitals can treat all trauma cases, only two - KK Women's and Children's Hospital and the National University Hospital - are fully equipped to treat children.
The MOH and SCDF explained yesterday that SCDF emergency ambulances take patients with severe trauma to the nearest accident and emergency (A&E) department that is equipped with the necessary resources, equipment and specialist medical support to deal with such complexities of care.
In this case, TTSH was the nearest such hospital, not Mount Elizabeth Hospital.
"In addition, as part of pre-hospital medical care management, all SCDF emergency ambulances are equipped with the necessary medical equipment and manned by well-trained paramedics and crew that are capable of performing resuscitation on patients," the authorities said.
SCDF took the six victims to TTSH in five ambulances.
TTSH was alerted by the first SCDF ambulance to be on standby to receive the patients.
Mount Elizabeth Hospital's chief executive Noel Yeo said in a Facebook post on Monday that the hospital's 24-hour emergency department is open to all patients, regardless of who they are, and the hospital will dispatch staff to attend to emergencies via its ambulance service.
Dr Yeo said the hospital's A&E team would have responded immediately had it been activated or informed of the incident on Sunday.
The MOH spokesman said yesterday: "MOH is happy to work with the private hospitals to establish the minimum standards that they should meet, should they wish to upgrade their suite of clinical services to provide emergency care services in the future."