Geologists have been left baffled by this extraordinary fiery hole which has opened up on the side of a Chinese mountain.
The small hole has been glowing bright orange due to its intense heat since it was spotted a week ago by builders and villagers in Urumqi, the capital of Xinjiang Uyghur Autonomous Region.
The area was sealed off as mining experts and geologists were called to the area.
Geologist Hu Tan who is leading the investigation into the 80 cm wide hole said: 'The air blasting out of the hole is so hot, that if you hold a branch near to it it bursts into flames.
'Although it is unusual, we're pretty certain that it has been caused by the spontaneous combustion of coal.'
His colleague, mining expert Cao Jianwen, said the area used to be a coal mine back in the 1970s, and there were documented examples of similar phenomena from previous years.
He said: 'We have recorded a temperature of around 792 degrees Celsius, which is pretty hot and I can understand that locals are superstitious.'
After the cause of the unusual event was identified, authorities moved in to fill in the hole and seal it off, saying they were worried that fumes could be harmful to anyone working in the area if they were forced to inhale them for long periods.
Jianwen added: 'I would not rule out that there could be similar sinkholes in this region in the future, and we should be contacted immediately if others are discovered so proper measures can be taken to either close of the hole or seal the area.'