The active search for the remaining missing crew member from a Japanese commercial ship that caught fire earlier in the week has been suspended, the U.S. Coast Guard said Thursday.

Twenty of the vessel’s 21 crew members had been accounted for as of Wednesday after the fire started Monday on the 59,400-ton Sincerity Ace, which was carrying 3,500 Nissan Motor Co. vehicles from Yokohama to Hawaii.

After “good Samaritan” crew from merchant vessels rescued 16 people Monday, an additional four were found “unresponsive and unable to grab onto life-saving equipment to be brought aboard,” according to the U.S. Coast Guard. They remain in the water until commercial tugboats arrive at the scene.

“Following the conclusion of morning and afternoon searches by our aircraft and commercial vessels we suspended the active search. This is always a difficult decision and takes many factors into account,” said Chief Petty Officer Dennis Vetrano of the Coast Guard Joint Rescue Coordination Center Honolulu.

“We extend our condolences to the families and loved ones of the crew members affected by this tragedy.”

The fire broke out on New Year’s Eve when the Panama-flagged car carrier was traveling about 3,330 kilometers (about 2,000 miles) northwest of Oahu Island. As of Thursday, the vessel remained adrift and burning, according to the Coast Guard.

“We have no information on the condition of the vehicles at this time,” said Nissan North America spokeswoman Lloryn Love-Carter. “Our thoughts are with the crew members as well as the safety of the rescue teams.”

The 21 crew members are Philippine nationals, according to the ship’s managing company, Shoei Kisen Kaisha. The company has dispatched commercial tugboats, which the Coast Guard said will arrive Monday, to transport the survivors and make recovery efforts.

The cause of the fire and the conditions of the unresponsive crew members remain unknown.