The NSW Environment Protection Authority (EPA) said it was investigating after local landholders reported the blast fume.

EPA director north Gary Davey confirmed on Friday the EPA was already following up on the landholders’ reports. 

“The EPA is undertaking an investigation into the incident, including analysing video footage taken by the mine operator of the fume event,” he said. 

“The EPA understands that the blast resulted in a fume event that travelled over land owned by Whitehaven mine.

“At this point, the EPA has no evidence there was any environmental harm, however this will be part of the investigation.” 

Mr Davey said blast fumes happened when variations in blast conditions, blasting products and geological factors combined to cause incomplete combustion and produced gases including nitrogen oxides which often were orange in colour.

Whitehaven was  fined and warned by the EPA in 2012 for polluting waters and breaching its environment protection licences at its Narrabri and Tarrawonga coal mines.

“The EPA is very concerned by the number of incidents that have occurred and has formally put Whitehaven Coal on notice to improve its environmental performance,” Mr Gifford said at the time.

Two penalty notices were issued as a result of an incident in November 2011, when water from a sediment dam at the Narrabri Coal mine overflowed and up to 0.6 megalitres entered Kurrajong Creek tributary. 

The Tarrawonga Coal mine was also issued with two penalty notices over a sediment discharge that happened in January 2012.

Whitehaven Coal was also found by the NSW Environment Protection Agency to have breached its annual Tarrawonga two million-tonne limit for coal output by 136,045 tonnes in the 2013-14 financial year.

Maules Creek Coal Mine officially opened in February this year.

It is expected to employ 450 people when it reaches full production.