The astonishing footage captures the surreal moment purple smoke billowed from a fertiliser factory causing health concerns among residents in China.

The series of clips recorded in the city of Zhumadian in Henan province show the oddly-coloured smoke emerging from the chimneys of the Henan Junma Chemical Industry chemical plant on February 14.

In one scene a colossal cloud can be seen forming over the surface of a local lake and casting a massive purple shadow over its waters.

Another scene depicted individual driving around town and recording the sight with their smartphone. A third clip showed a person filming the incident from their apartment building.

Stunned over the sight, locals immediately turned to social media questioning whether the released gas was potentially toxic.

Henan Junma Chemical Industry staff said: 'During that period, the company was engaged in equipment maintenance, during which they transferred the gas intended for replacement into a torch for controlled combustion.

'The released gas was confirmed to be non-toxic and posed no harm.'