Islamic State militants set fire to four oil wells in Qayyara, south of Mosul before abandoning the city in mid August, according to Reuters.

The first images captured by NASA, showed black smoke pluming south of Mosul as the fire steadily continued to burn, citing the oil wells as the most likely source of smoke, reported The Time.

The Iraqi military recapture of Qayyara, along with a nearby airbase, in an attempt to reclaim Mosul, the largest city under Islamic State control. The militants extracted oil from some 60 wells in the city and sold it to help finance its activities.

Islamic State used to ship at least 50 tanker truckloads a day from Qayyara and nearby Najma oilfields to neighboring Syria. A sign remains on the main road announcing prices of crude in places like the Syrian city of Aleppo, 550 km west of Qayyara.

The smell of petrol now overwhelms the area, wind carrying the smoke from well fires into the town center.