Eleven crew members of a Hong Kong-flagged bulk carrier are missing after their ship sank Friday off the coast of Philippines in what appears to be a possible case of nickel ore liquefaction.

The Japanese Coast Guard reported Friday it had received a distress call from the 57,000 dwt MV Emerald Star, which was sailing about 280 km east of the northern tip of the Philippines with a crew of 26 Indian nationals.

Three vessels in the area were able to rescue 15 crew members but 11 others are still reported as missing, the Coast Guard said, adding that the ship has sunk.

According to the S&P Global Platts, the Emerald Star was underway from Buli, Indonesia to Lianyungang, China with a cargo of nickel ore.

Nickel ore, a high-risk Group A cargo in the International Maritime Solid Bulk Cargoes Code, is notoriously known to be highly susceptible to liquefaction, that is when a dry cargo becomes fluid (i.e. liquefies) typically when exposed to an excessive amount of moisture. Cargo liquefaction can lead to cargo shift and vessel stability issues, and in the worst case can cause a ship to capsize at a moments notice.

For this reason, nickel ore is often regarded as the world’s most dangerous cargo as dubbed by INTERCARGO, which represents the interests of dry cargo ship owners and operators.

Shipping nickel ore from Indonesia to China is known to be particularly risky. In fact, nickel ore liquefaction was cited as the cause of at least four vessel casualties and the loss of 66 seafarers in the trade from October 2010 to December of 2011. And in 2013, the phenomenon was blamed for the loss of the MV Trans Summer, which sank off the coast of Hong Kong while carrying 57,000 tons of nickel ore loaded in Indonesia.

The number of vessel casualties blamed on nickel ore liquefaction has fallen in recent years in part due to an export ban on nickel ore and bauxite from Indonesia, which was imposed in 2014 in order to boost Indonesia’s higher value smelting industries. Earlier this year, however, Indonesia introduced new rules to ease the 3-year export ban under certain conditions.

Following the easing of the ban, INTERCARGO issued a statement to its members in January 2017 warning them of the risks associated with these types of cargoes:

“We would urge Members exercise extreme caution should Indonesian ore exports re-enter the market; as the ban has been in place for some time it is most likely that many stockpiles will be subject to saturation and therefore the possibility of being offered cargoes with an unduly high moisture content may be anticipated. Furthermore, it is important to note that it has been reported specified shippers will be permitted to export washed bauxite, this form of processing of cargo was associated with a number of problems in the past and any such cargoes should carefully assessed prior to acceptance,” the statement said.

The 2010-built MV Emerald Star is registered in Hong Kong and operated by Stellar Ocean Transport of Dubai.