Volunteers in Mauritius are scrambling to create cordons to keep leaking oil from a tanker away from the island.
Locals are making absorbent barriers of straw stuffed into fabric sacks in an attempt to contain and absorb the oil.
Mauritius is home to world-renowned coral reefs, and tourism is a crucial part of its economy.
Images posted online by local media show volunteers collecting straw from fields and filling sacks to make barriers.
Their actions go 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.
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.
It is thought that the ship, registered in Panama, had some 4,000 tonnes of fuel aboard when it ran aground. All crew were evacuated.
At least 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 ship 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”.
In 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.
France has sent a military aircraft with pollution control equipment from its nearby island of Réunion.
On Sunday, Japan announced it would dispatch a six-member team to assist the French efforts.
Mr Jugnauth is set to hold an emergency meeting later on Sunday amid fears that bad weather could further complicate efforts to hold back the oil.