Fears that oil may be seeping from the sunken tanker Sanchi arose as clumps of oil appeared on the shores of southern Japan, Reuters said citing Japanese Coast Guard.

The clumps washed up on the shores of the island of Amami-Oshima, while the coast guard and Kagoshima Prefecture confirmed that black oily substances were found drifting off the shore of the small island of Takarajima, local media reports. The substance was reportedly found on other beaches on the coastline facing the East China Sea.

There is still no official confirmation that the oil is leaking from the Iranian-flagged Sanchi, which sank in the East China Sea on January 14. The vessel capsized some 530 km from Shanghai and 310 km from Naha, Japan, following a collision and a number of explosion aboard the ship. The vessel lies at a depth of around 115 meters.

At the time of the incident, Sanchi was carrying 136,000 metric tons of ultra-light, highly flammable condensate. Chinese maritime authorities earlier said they detected four oil slicks at the site of the Sanchi wreck encompassing a total of 101 square miles.

The government of Japan established a special unit to monitor the oil spill in an effort to determine the exact cause and the extent. Relevant authorities launched clean up operations in the affected areas.

A recent ocean model simulation research from University of Southampton and National Oceanography Centre (NOC) estimated that oil spilled from Sanchi could reach Japan by mid-February. In addition to the Amami Oshima area, the coastlines of northern and southern Kyushu as well as waters off Shikoku and off Yamaguchi and Shimane prefectures, faced varying degrees of risk from it.

“However, the fate of the leaking oil is highly uncertain, as it may burn, evaporate, or mix into the surface ocean and contaminate the environment for an extended duration,” NOC said.