Rescue teams called off the search for the three-man crew of a yacht found drifting off the northeast coast of Australia even as the mystery of their disappearance deepened yesterday.

Analysis of the 40ft (12 metre) catamaran’s instruments showed that she had not been steered since last Sunday, when she was heading for an area of building seas and squalls.

Police were working on the assumption that the three middle-aged men had been washed overboard by a large wave, but officials said they were surprised that the boat and its contents were otherwise undisturbed.

Investigators could not discount other theories for the disapppearance of the owner, Derek Batten, 56, and his crew, James Tunstead, 63 and his brother Peter, 69.

The Australian crew’s wallets and mobile phones were lying on the chart table, the dining table was set, the engine was running and the computer was on, and shorts, T-shirts and sunglasses were neatly folded on the aft deck, as if the men had gone for a swim.

And yesterday it emerged that the yacht’s fenders — “bumpers” used to cushion against other boats or jetties — were hanging from one side of the boat, raising suspicions that another vessel had come alongside the Kaz II before her crew went missing.

The yacht was seen from an aircraft, drifting about 50 miles off northern Queensland on Wednesday. When rescuers reached her the next day, they could find no sign of the crew and the only damage was a shredded sail. The extensive air and sea search was called off yesterday afternoon.

While police favoured the theory that the three had been lost overboard in stormy weather, they could not discount other theories including the forced removal of the men or the possibility that they died after one fell overboard and the others tried to save him.

Phil Livingstone, one of the helicopter rescue crewmen involved in the boat’s retrieval, told Sydney’s Sunday Telegraph: “There were neatly placed shorts, sunglasses and a cap sitting on the back deck, unruffled like they had just gone for a swim.

“What is bizarre about this is it looks like — the sails are shredded — it looks like it’s turned turtle, but everything is in place.”

The theory that the men may have been lost trying to save a man overboard gained credence with the discovery that although the yacht’s engine was running it was in neutral and the propeller shaft was not engaged. Experienced yachtsmen said that neutral would be selected if crew were trying to retrieve someone.

Relying on course data from the Global Positioning System aboard the Kaz II, police believe she had not been steered since late in the afternoon of Sunday April 15. On that morning she left Airlie Beach, south of Townsville, on the first leg of a journey intended to take her across Australia’s vast northern coast and then down the West Australian coast. The GPS data show she was steered northeast into a region where squalls and rough seas were building. By Sunday night, the data show her drifting.

“It seems very unlikely we will be able to say exactly just what has occurred at this point in time,” said Inspector Warren Webber, of the Townsville police.

The theories

Theory one

The Kaz II sailed into stormy weather. Crew washed overboard in rising seas

Theory two

One crew member fell overboard or went swimming in calm seas. The other two crew members drowned while attempting a rescue

Theory three

All three crew taken by sharks while swimming

Theory four

Rogue vessel came alongside and kidnapped crew of Kaz II

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