Fourteen ships have been identified as possible sources of a film of oil stretching, in broken sections, 30 kilometres long and five kilometres wide south of Townsville, Patrick Quirk, general manager of Maritime Services Queensland said on Saturday.

An oil slick was confirmed 18 nautical miles (33 kilometres) NNE of Cape Upstart on Friday evening, but was broken up into metre-sized blotches of oily film by the weather.

Authorities are investigating 14 possible sources of an oil spill near the Great Barrier Reef. Credit:File/Jessica Shapiro

"We know the ships that went past the area," Mr Quirk said.

"There are 14 ships that we consider are possible sources of oil and we plan to take oil samples from all of those ships," he said.