National Sea Rescue Institute This is the massive Stellar Daisy which officials fear has sunk in the South Atlantic.

A frantic search has begun to locate 22 crew members of a massive South Korean cargo ship that sank in the South Atlantic over the weekend.

Two Filipino crew members stranded in a life raft were rescued on Saturday. Authorities spotted the raft after an official on board the 1,020-foot freighter known as the Stellar Daisy texted the vessel’s South Korean owner, Polaris Shipping, that it was taking on water. At the time, the freighter was about 1,500 miles off the coast of Uruguay, Reuters reported.

Other life boats were seen in the water as well, but they were empty, South Korea’s Yonhap news agency reported on Sunday. Searchers also spotted fuel and debris in the water.

“A ship observed an oil sheen and debris in addition to smelling a strong petroleum odor, which indicates that the stricken vessel has sunk,” the Uruguayan navy said in a statement.

“The more hours pass, the less the chances are of finding” survivors, a spokesman for the navy told Reuters.

According to the Fleetmon maritime news site, one of the rescued crewmen said he went to the starboard deck wearing a life vest when the freighter began listing about 15 degrees. Several other seamen, also in life vests, were gathered on the deck when the crewman spotted several cracks in the ship. He watched as at least one crew member jumped into the water and swam away from the ship. The vessel reportedly capsized very quickly, broke apart and sank.

The Uruguayan navy alerted merchant ships in the area about the incident, and a search for the missing freighter was launched.

“A search operation is continuing for the 22 people,” said a South Korean foreign ministry official. Eight of the missing crew members were South Korean nationals, and 14 were Filipino.

South Korea has asked for additional help from the Brazilian navy. A Brazilian destroyer with a rescue helicopter is steaming to the scene, and is expected to arrive on Tuesday.

The cause of the capsize was not known; however, the weather was calm and likely didn’t play a role.

When it disappeared, the freighter was hauling iron ore from Brazil to China.