Aircraft have sprayed chemicals to break up a large oil slick off Australia's northwestern coast as environmentalists expressed fears for rare wildlife from oil gushing into the sea from an uncapped well.
The Australian Maritime Safety Authority said the slick from the West Atlas offshore drilling rig had lengthened from an estimated 15kms on Saturday.
The first sortie of chemical dispersant sprayed on Sunday from a C-130 Hercules aircraft appeared to have started to break up the slick, a spokeswoman said.
But the clean-up cannot be completed until the well is capped, which experts say may take months.
Rig operator PTTEP Australasia, a unit of Thailand's PTT Exploration and Production PCL, has flown in a team of experts to try and determine how to cap the well, which first began to leak oil and gas on Friday.
An air exclusion zone has been set up and ships have been advised to stay more than 20 nautical miles away from the rig, which is currently considered too dangerous to board.
Environmental group WWF called for changes to preparations for such disasters, pointing out it took three days for the first dispersant to be sprayed, although the region is considered a critical area for biodiversity.
WWF Australia's director of conservation Gilly Llewelyn said among the animals affected were sea snakes and three endangered species of turtles.
A national clean-up plan has been activated to deal with the spill, which occurred at the Montara development, a project due to come on stream later this year.
The West Atlas drilling unit is owned by Norway's SeaDrill Ltd, but operated by PTTEP Australasia.
The location of the spill is about 250km off the far north Kimberley coast of Western Australia, and 150km south-east of Ashmore Reef, a small Australian offshore possession.
Australia's official overseer for the petroleum industry, the National Offshore Petroleum Safety Authority, was investigating the incident.
