Emergency workers assess the scene of a blaze at Pakistan Institute of Medical Science in Islamabad on Wednesday that killed at least 14 newborn babies. Photo by Sohail ShahzadEPA

Aug. 26 (UPI) -- At least 14 newborn babies were killed early Wednesday after fire swept through the maternity department of one of the largest public hospitals in Islamabad.

One baby was among 19 people rescued from the Pakistan Institute of Medical Sciences in downtown Islamabad after the fire started in an air conditioning unit in the third floor ward, which was then fueled by oxygen being administered to babies in incubators, or directly.

Health Minister Mustafa Kamal told GEO news that the incident, which occurred at 6:45 a.m. local time, was caused by a "blast in the air conditioner," with the explosion igniting a blaze which was made more intense due to the presence of oxygen tanks.

Expressing "deep sorrow and heartfelt regret," Pakistani Prime Minister Shehbaz Sharif said in a statement issued by his office on X that he had ordered "an immediate investigation" into the tragedy.