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.

Supplied photo shows a member of a disaster relief team investigating the oil on mangroves on Aug. 22, 2020. (Photo courtesy of Japan International Cooperation Agency)(Kyodo)

"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.

While no dead or dying mangroves have been found so far, the team said oil coating on the pneumatophores of mangroves has been confirmed in all seven surveyed locations, with a wide area of damage found in two sites.

Clearing oil from mangrove forests in a muddy environment, instead of a rocky one, is particularly difficult as the removal work may allow deeper penetration of the oil beneath the forests, according to the team.

The group will start assessing the impact of oil spill on the Ramsar wetlands near the accident site on Thursday.

The bulk carrier Wakashio transporting a total of some 3,800 tons of fuel oil and 200 tons of diesel, operated by Mitsui O.S.K. Lines Ltd., ran aground near Pointe d'Esny on July 25, and more than 1,000 tons of oil began leaking from the vessel on Aug. 6.

Following the incident, JICA dispatched last week the second batch of members of the Japan Disaster Relief team to Mauritius.

Environment Minister Shinjiro Koizumi told a press conference Tuesday that the ministry is considering sending additional environment experts to the island nation.

The second team has inspected 12 locations near the shipwreck, finding no apparent coral deaths caused by the oil spill and no evidence of oil on the seabed. However, ropes containing the spill and the wreck of the ship have destroyed corals, according to a team official, and the water near the accident site is murky as a result.

The front section of the ship was towed to open water and sunk as instructed by local authorities after the wreckage was broken into two.

"If turbidity continues for a long period of time, it will put stress on corals and could kill them," Sakaguchi said, adding the team will continue to monitor the situation and take measures to deal with it.

Related coverage:

Stranded ship neared Mauritius to get mobile network for virus info

Japan criticized for weak presence in responding to oil leak in Mauritius

Mauritius arrests captain of Japan-owned ship that leaked oil