Staff from the regional and city councils then found oily residue along the high tide mark of the new tidal steps on The Strand waterfront and on several locations around Sulphur Point's new Marine Precinct.
Sites where oil had washed up on Tuesday were checked again following the tidal cycle yesterday morning.
''Staff did spot a small sign of oil as far south as Memorial Park,'' he said.
Harrex said a further report was received yesterday from a member of the public who found a small amount of oil near Second Ave.
The regional council had a boat on the water yesterday inspecting oil booms placed around where oil had washed up at the Marine Precinct.
The public cordon around the tidal steps was left in place overnight Tuesday to allow a final check yesterday morning.
Harrex said investigations found no link with the pipeline that failed as part of the Mobil oil spill in 2015.
An oil boom was also placed around the tidal steps to try and stop the oily residue spreading further and to allow the clean-up to commence.
He declined to go into details of the ongoing investigation to discover the source of the spill. ''It is inappropriate to comment on the details.''
The regional council asked people who found further deposits of residue to use the pollution prevention hotline 0800 884 883.
Areas of harbour polluted by oil spill
- Marine Precinct next to Harbour Bridge
- The tidal steps, downtown waterfront
- Bottom of 2nd Avenue
- Memorial Park
