A least 15 infants were killed after a fire broke out at the maternity ward of a hospital in Islamabad, Pakistan, on Wednesday.

"A fire broke out on the third floor of the MCH Ward at PIMS Hospital," the district office of Islamabad said.

Officials said 16 newborns were in the ward at the time, adding that one was rescued.

The cause of the fire was likely due to a malfunctioning air conditioning unit, rescuers said.

Investigation underway