At least 15 newborns lost their lives at the maternity clinic of a public hospital in Islamabad when a fire broke out due to a technical malfunction in an air-conditioning unit, local television network Geo TV reported, while local authorities in Pakistan’s capital put the death toll at 14 infants.

The fire at the Pakistan Institute of Medical Sciences (PIMS) broke out two hours ago, Geo TV added, noting that firefighting operations are still underway.

There were 16 newborns in the hospital’s maternity clinic when the fire broke out, and one of them was rescued, the television network reported.

Local authorities, for their part, said in a statement that “a fire broke out on the third floor of the maternal and child health clinic at PIMS hospital.”

“A total of 14 children lost their lives in the incident,” they added.

This is the deadliest fire to have broken out at a hospital in Pakistan in recent years.

Pakistani Prime Minister Shehbaz Sharif called on authorities to launch an immediate investigation, his office said. “Those responsible must be identified and the strictest measures must be taken,” he stressed.