Asbestos has been found at five more parks and reserves in Melbourne's west, with the source for most sites confirmed as historic dumping or legacy contamination.
The Environment Protection Authority was notified of the discoveries by Hobsons Bay City Council, taking the council's total affected sites to 14.
The new sites are Buffer Mound in Altona, Grieve Parade and Kororoit Creek Reserve in Altona North, Newport Lakes Reserve in Newport and Truganina Park in Altona Meadows.
"The notification marks the end of Hobsons Bay City Council's current assessment of parks and reserves that have received recycled mulch," the watchdog said in a statement on Thursday.
"Of the 21 sites inspected, seven have been cleared as being free of asbestos.
"EPA and Hobsons Bay City Council have determined the likely source of contamination at all but two of the 14 affected parks as being historic dumping or legacy in situ contamination."
Donald McLean Reserve in Spotswood and Kororoit Creek Reserve remain without a confirmed source of asbestos contamination.
The watchdog will keep looking and forensically examine the council's mulch supply chain, concentrating on contamination risk controls in the transport, handling and laying of mulch.
"EPA reiterates that its inspection of three mulch producers that supplied Hobsons Bay City Council parks showed they have appropriate controls to prevent contamination in the end product," it said.
Asbestos was found at another three Melbourne sites across separate councils in April but each has since been remediated and cleared.
LIKELY SOURCE OF CONTAMINATION AT MELBOURNE'S 17 IMPACTED SITES:
Hobsons Bay City Council:
Altona Coastal Park, Altona - historic dumping
Buffer Mound, Altona - historic dumping
PA Burns Reserve, Altona - legacy in situ contamination
Crofts Reserve, Altona North - legacy in situ contamination
Doug Grant Reserve, Altona - historic dumping
Grieve Parade, Altona North - legacy in situ contamination
GJ Hosken Reserve, Altona North - legacy in situ contamination
Kororoit Creek Reserve, Altona North - uncertain
Laverton Creek (rear of AB Shaw), Altona Meadows - historic dumping
PJ Lynch Reserve, Altona North - historic dumping
Donald McLean Reserve, Spotswood - uncertain
Newport Lakes Reserve, Newport - legacy in situ contamination
Truganina Park, Altona Meadows - legacy in situ contamination
Brimbank Council:
Fitzgerald Square Reserve, Sunshine West - historic dumping
City of Casey Council:
Minihans Reserve, Cranbourne - historic dumping
Merri-bek City Council:
Shore Reserve, Pascoe Vale South - nearby building works