The Hong Kong-flagged cargo ship Jin Tian sank off southwestern Japan and efforts are underway to rescue some of the 22 crew members.

The vessel sank 110 kilometers west of the remote Danjo islands early morning Wednesday, part of Nagasaki prefecture, a Japan Coast Guard spokesman said, confirming an earlier Kyodo News report. The coast guard received a distress call at 11:15 p.m. Tuesday, he said, adding the cause of the ship sinking was still unknown. 

Five Chinese nationals were rescued from the ship, Japan’s Chief Cabinet Secretary Hirokazu Matsuno told reporters in Tokyo.

According to vessel data analyzed by Bloomberg, the ship loaded a cargo from Papua New Guinea in early January and was headed for South Korea’s Incheon port. The maximum draft of the ship is 7.7 meters and the last reported draft was 8.3 meters, according to data from IHS Markit. The ship carried hardwood, Yonhap News Agency reported. 

IHS Markit data shows that the beneficial owner of the ship is Shenzhen Shekou Shipping Transportation Co. The company, listed on the Beijing-based National Equities Exchange and Quotations, didn’t immediately reply to email seeking comment. China’s financial markets are closed for the Lunar New Year holiday.

The incident, coming during an unusually frigid week in Japan, appears to be the worst since a cargo ship carrying almost 6,000 cattle sank in 2019 off the coast, leaving most of the crew of 39 missing at sea.  

The Jin Tian crew consisted of 14 Chinese nationals and 8 from Myanmar, the coast guard said. They boarded emergency rafts at 2:40 in the morning, and the ship went under six minutes later, they added.

Three civilian ships — a Japanese research vessel, a Liberian tanker and Chinese cargo ship — are undertaking rescue efforts, maritime authorities said, adding that the coast guard and Japan Self-Defense Forces were en route.