Fire and Rescue NSW (FRNSW) worked from 10.30am, in conjunction with the NSW Environmental Protection Authority (EPA) and Dubbo City Council to clear the substance.

The HAZMAT team cleaned about 60 litres of the substance from under the Emile Serisier Bridge.

Boons and a skimmer pump cleared the substance from the river by 1pm,  according to FRNSW Dubbo station commander Mark Weir.

The source of the substance is unknown but it is believed it may be linked to the stormwater lines in Erskine Street.

Station commander Weir said the substance was not enough to contaminate the Macquarie River.

“There was only a small amount of oil on the river, which was too fine to worry about,” he said.

“There has been no damage to the water supply thanks to swift action.”

Two days before the incident the SES and FRNSW held a joint exercise on the banks of the river , which simulated a similar situation.

The exercise required the installation of boons with a boat and the operation of a skimmer pump, both of which were used to 

eliminate the substance from the area yesterday.

Station commander Weir said the EPA investigated businesses on Erskine Street and could not identify where it came from or what it was.

The EPA could not provide further details by time of print.