The fire was so huge that its flames be seen even from some areas in Rawalpindi.
The official said that another fire which had broken out on Saturday was extinguished on Sunday morning.
Responding to a question about the area affected by the fires, he said the extent of loss could be ascertained only after the flames had been put out. The official said the CDA staff had been trying to put out the fire for 36 hours.
Margalla Hills, which falls in the National Park limits, witness on an average 50 incidents of fire a year, especially between April and July.
Environmentalists expressed concern over negligence of the authorities in preventing fires which damage natural forests, wildlife and the ecosystem.
They called for long-term measures to save the already depleting forests of Margalla Hills.
An official of the Pakistan Environment Protection Agency (Pepa) said sometimes the fire broke out due to internal combustion. In some cases, throwing of matches and cigarettes by visitors caused fire, he added.