ISLAMABAD (AP) — Investigators appointed by Pakistan's prime minister were making a visit Thursday to the hospital nursery where a fast-moving fire killed 14 newborns, as grieving families and the public sought answers about the cause of the blaze and the safety measures at the major government facility.

The fire early Wednesday was confined to the third-floor nursery and did not affect the rest of the facility. Hospital officials said the fire spread so quickly the two doctors, two nurses and other staff present were able to rescue only one baby among the 15 in the nursery.

The scene at the Pakistan Institute of Medical Sciences in Islamabad was somber Thursday as doctors, staff, patients and relatives mourned the newborns. Access was restricted to the third-floor area where the fire occurred.

Prime Minister Shehbaz Sharif appointed the investigating committee, led by retired federal secretary Shahid Khan. They are expected to take statements from hospital staff, witnesses and families. The committee is expected to make urgent recommendations to Sharif within 48 hours and deliver a comprehensive report within five days.

Hospital and district officials initially said an exploding air-conditioning unit caused the fire. In its preliminary report, however, the hospital said a blast involving a nebulizer sparked the blaze, which spread within minutes because of the high concentration of oxygen in the nursery. The committee has not reached its own conclusion and will independently determine the cause, the city administration said.

Authorities handed over the bodies of all 14 newborns to their families overnight.

The deaths prompted authorities to order broader reviews of fire-safety measures and firefighting equipment at hospitals. In Punjab, Pakistan's most populous province, the government instructed the Health Department to immediately review fire-safety systems and emergency-response facilities, according to a government statement.

Sharif dismissed Health Secretary Aslam Ghauri, the Health Ministry's highest-ranking civil servant, after the fire. Grieving parents have demanded answers about how the fire began and whether the nursery had adequate firefighting equipment.

The U.N. children's agency, UNICEF, said it was saddened by the deaths and called for an urgent review and strengthening of fire-prevention and safety standards at health facilities.

The fire was among Pakistan's deadliest recent tragedies involving children. In June, 14 schoolchildren were killed when the roof of a tutoring center under construction collapsed in the eastern city of Lahore.