Heavy winds of 50km/h (31mph) in Mauritius have put efforts to remove leaking oil from a ship on hold until Monday evening.
The MV Wakashio, believed to have been carrying 4,000 tonnes of fuel oil, ran aground on a coral reef off the Indian Ocean island on 25 July.
Huge waves up to 5m in height are also expected on Monday.
Mauritius is home to world-renowned coral reefs, and tourism is a crucial part of its economy.
Images posted online by local media on Sunday showed volunteers collecting straw from fields and filling sacks to make barriers against the oil.
Volunteers have been trying to absorb the oil using barriers of straw
Others had been making their own tubes with tights and hair to add to the effort and some have been cleaning up the island’s beaches.
Their actions went against an order from the government asking people to leave the clean-up to local authorities.
“People have realised that they need to take things into their hands. We are here to protect our fauna and flora,” environmental activist Ashok Subron told AFP news agency on Sunday.
Mitsui OSK Lines, the operator of the ship, said it had tried to place its own containment booms around the vessel but had not been successful owing to rough seas.
Helicopters have been attempting to move some of the fuel and diesel off the ship.
It is thought that the bulk carrier, registered in Panama, had some 4,000 tonnes of fuel aboard when it ran aground. All crew were evacuated.
More than 1,000 tonnes of oil is thought to have leaked into the waters surrounding the island nation.
Environmentalists are concerned about the impact on the country’s ecosystem.
The MV Wakashio ran aground at Pointe d’Esny, a known sanctuary for rare wildlife. The area also contains wetlands designated as a site of international importance by the Ramsar convention on wetlands.
Happy Khamule from Greenpeace Africa warned that “thousands” of animal species were “at risk of drowning in a sea of pollution, with dire consequences for Mauritius’ economy, food security and health”.
Satellite images show the extent of the oil spill
At a news conference, Akihiko Ono, executive vice-president of Mitsui OSK Lines “profusely” apologised for the spill and for “the great trouble we have caused”.
He vowed that the company would do “everything in their power to resolve the issue”.
Police in Mauritius say they have been granted a search warrant, allowing them to board the vessel take away items of interest such as the ship’s log book in order to help with an investigation. The ship’s captain will assist officers with their search.
On Friday, Mauritian Prime Minister Pravind Jugnauth declared a state of emergency and appealed for help.
Volunteers are trying to limit the damage caused by the oil spill
France has sent a military aircraft with pollution control equipment from its nearby island of Réunion.
On Monday, Japan sent a six-member team to assist the French efforts.