A Japanese disaster relief team said Tuesday the oil spilled from a grounded Japanese freighter off Mauritius in the Indian Ocean could kill mangroves if it is not cleaned up soon.

The team composed of seven members, including five environment experts, has been conducting an on-site probe of the damage to the environment, especially the mangrove forests and coral reefs, since Friday, while providing on-site environment assistance to the Mauritius government.

"In the heavily polluted areas, oil adhesion to pneumatophores (or aerial roots) can suffocate mangroves to death. Also, if the oil stays for long, its toxic substances can kill mangroves," Noriaki Sakaguchi, vice team leader and an ecosystem conservation expert at Japan International Cooperation Agency, said in an online briefing.