Fire and Rescue NSW crews were called to the scene, near Gardiner Street, about 7.30am Thursday after a member of the public reported an oily substance in the creek.

Lower Hunter zone commander Superintendent Greg Windeatt said the contaminant was a hydrocarbon, ­oil-based material.

He said the source of the spill was unknown.

A hydrocarbon compound had been detected in wind gusts at Rutherford on Thursday, but Superintendent Windeatt said there was no danger to people’s safety.

“We have done all our appropriate atmospheric monitoring and we are not receiving any low explosive limits, so it’s not within a flammable range,” he said.

“There is no risk to public well-being, but we’ll continue to monitor that.

“It’s quite a large area, it’s definitely a large quantity, but it’s difficult for us to estimate the precise amount.”

Rain made the job more difficult for clean-up crews because downpours caused water to run along the creek and spread the oil. 

Superintendent Windeatt said there was no indication how long the oil had been in the water.

Paramedics were on standby as a precaution because of a pungent odour from the spill.

Hazardous materials specialists stopped the oil from spreading using hydrocarbon beams and fence posts.

They scraped the floating subtance off the surface of the water and loaded it into a waste truck.

The clean-up effort is expected to be completed Friday morning.

“We are not going to operate while it is dark because, being a creek in the bush, it is unsafe,” Mr Windeatt said. 

“Particularly with the mud and rain, it has been very slippery.”

Environmental Protection Authority analysts tested samples of the material.

They will take samples from the nearby businesses to try to find a match and identify the source of the spill.

EPA Hunter Region manager Adam Gilligan said the water entered the creek through a stormwater drain.

“Our officers have taken a number of samples of the material to try to identify the source and will be conducting interviews with owners and workers in the industrial estate,” he said.

“Any incident of this nature is a concern to the EPA and we will consider all the information available to us as part of our investigation.

“It is important all industries, especially those operating close to creeks or other sensitive environments notify the EPA immediately if an incident like this occurs.”

Anyone who has information about the spill is asked to phone the EPA environment line on 131 555.