Aircraft and ships ploughed through dire weather on Thursday in search of objects floating in the remote seas off Australia that Malaysia called a “credible lead” in the trans-continental hunt for the missing jetliner. 

The discovery of the floating objects was revealed by Australian Prime Minister Tony Abbott.“The task of locating these objects will be extremely difficult and it may turn out they are not related to the search for MH370,” he told Parliament.

The large objects, which Australian officials said were spotted by satellite four days ago in one of the remotest parts of the globe, are the most promising find in days as searchers scour a vast area for the lost plane.

The larger of the objects measured up to 24 metres (79 ft) long and appeared to be floating in water several thousand metres deep, Australian officials said. 

The second object was about 5 metres (16 feet) long. Arrows on the images pointed to two indistinct objects apparently bobbing in the water.

The Malaysian government said search would continue elsewhere despite the sighting in the southern Indian Ocean.

The area where the objects were spotted is around 2,500 km southwest of Perth, roughly corresponding to the far end of a southern track that investigators calculated the aircraft could have taken after it was diverted.

“Yesterday (Wednesday) I said that we wanted to reduce the search area. We now have a credible lead,” said Malaysian Transport Minister Hishammuddin Hussein.

The search that began in the tropical waters off Malaysia’s east coast has now switched to the vast, icy southern oceans between Australia, southern Africa and Antarctica.

Two Royal Australia Air Force AP-3C Orions, a US Navy P-8 Poseidon and a Royal New Zealand Air Force P-3K2 Orion were involved in Thursday’s search.

China’s icebreaker for Antarctic research, Xuelong (Snow Dragon), will set off from Perth to search the area, Chinese state news agency Xinhua cited maritime authorities as saying. 

The captain of the first Australian air force AP-3C Orion plane to return from the search area described the weather conditions as “extremely bad” with rough seas and high winds.

If the plane had run out of fuel, it would not necessarily have plummeted but its behaviour would have depended on whether there was someone in control and their intentions, the pilots said.

If the debris is from the plane, investigators would face a daunting task to retrieve the “black box” data and voice recorders needed to help understand what caused the disaster.