A federal investigation into an oil spill near the Great Barrier Reef has just about wrapped up, with all but a few possible culprits being ruled out.
Oil was found washed up on several Queensland beaches in July but the government is yet to pinpoint which ship was responsible.
The Great Barrier Reef Marine Park Authority told a Senate estimates hearing in Canberra on Monday that most of the 17 possible culprits had been ruled out after testing of their oil "fingerprints".
The authority confirmed 120 staff were deployed to the reef and beaches over a three-week period to clean up the spill, estimated to be around five to 15 tonnes of oil.
Authority chairman Russell Reichelt said there had been no other reports of washed-up oil and revealed the investigation had identified 17 vessels that could be responsible.
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Most had already been ruled out but legally the authority had to eliminate all other possibilities because oil fingerprints were not unique.
The investigation was expected to be completed within weeks and a brief of evidence would be provided to the director of public prosecutions to advise the best way to charge the culprit.
The vessels still under investigation were travelling globally, Mr Reichelt said.
