China is investigating new satellite images of debris in the southern Indian Ocean, potentially from missing Malaysia Airlines flight MH370, Malaysian officials say.

Malaysia’s acting transport minister read out the news as he was handed it during at his daily briefing, saying the debris was 30m by 22m.

He said the Chinese government would give more details on later today.

Flight MH370 dropped out of contact an hour after leaving Kuala Lumpur for Beijing on 8 March carrying 239 people.

The last 54 minutes of cockpit communication aboard the missing Malaysia Airlines flight MH370 was disclosed this morning in an exclusive story by the British newspaper, The Telegraph.

A transcript of conversations between the co-pilot and the control tower, and other air traffic controllers, runs from the time the Boeing 777 was taxiing to its last known position thousands of feet above the South China Sea.

It includes exchanges from a point at which investigators believe the plane had already been sabotaged, as well as the last words of Fariq Abdul Hamid, 27, the co-pilot: “All right, good night.”

Analysts said the sequence of messages appeared “perfectly routine”. However two features, they said, stood out as potentially odd.

The first was a message from the cockpit at 1.07am, saying the plane was flying at 35,000ft. This was unnecessary as it repeated a message delivered six minutes earlier.

But it occurred at a crucial moment: it was at 1.07am that the plane’s Acars signalling device sent its last message before being disabled some time in the next 30 minutes, apparently deliberately. A separate transponder was disabled at 1.21am but investigators believe the Acars was shut down before Hamid’s final, 1.19am farewell.

The other odd feature, one reason for suspicions that the plane’s disappearance was no accident, was that its loss of communication and subsequent sharp turn west occurred at the handover from air traffic controllers in Kuala Lumpur to those in Ho Chi Minh City.

“If I was going to steal the aeroplane, that would be the point I would do it,” said Stephen Buzdygan, a former British Airways pilot who flew 777s.

“There might be a bit of dead space between the air traffic controllers … It was the only time during the flight they would maybe not have been able to be seen from the ground.”

The fresh details add to speculation over the fate of MH370, whether it was the victim of a sudden accident or a hijacking. The transcript also suggests that if the pilots were involved, they were very careful to hide their true intentions.

Dozens of ships and aircraft continue to search an area off the Australian coast where debris, potentially from MH370, was spotted by a spy satellite earlier this week.

Malaysia has begun contacting the handful of nations with deep sea detection equipment for help in what may be a long search for the aircraft’s black box. The area of interest spans 9,000 sq miles of waters up to 13,000ft deep with strong currents.

Warren Truss, Australia’s deputy prime minister, acknowledged that the apparent debris may never be found. “Something that was floating on the sea that long ago may no longer be floating,” he said.

“It’s also certain that any debris or other material would have moved a significant distance over that time, potentially hundreds of kilometres.”

Search planes from Australia spent 10 hours scouring the area until nightfall on Friday.

Malaysia has asked the United States for undersea surveillance technology, Pentagon officials said.

Hishammuddin Hussein, Malaysia’s acting transport minister, said that the search was proving frustrating and cautioned: “This is going to be a long haul”.

“We have to trench down and the focus is to reduce the area of search and possible rescue,” he added.

Malaysia Airlines disclosed on Friday that the aircraft was carrying some lithium ion batteries, which are deemed “dangerous” cargo and can overheat and cause fires.

They have been responsible for 140 incidents on planes in the last 23 years according to the US Federal Aviation Administration, including one when a UPS cargo plane crashed during an emergency landing in 2010.

But Ahmad Jauhari Yahya, the airline’s head, said that the batteries, which are used in laptops and mobile phones, were packed and carried in accordance with regulations and were unlikely to have posed a threat.

He has previously revealed that Hamid, the co-pilot, spoke the final message on the plane but he would not comment yesterday on whether Hamid appeared to have been under duress.

According to the cockpit transcripts, from the moment of sign-in at 12.36 when the plane was still on the ground, Hamid, a 27-year-old flying enthusiast, gave routine accounts of its location, ascent and altitude.

Although he took a slightly casual approach and at times departed from formal wording, nothing in his banter gives any sign that the plane was about to fly off course and disappear.

Some experts said that they did not see anything to make them feel something sinister might have been going on.

The Telegraph has repeatedly asked Malaysia Airlines, Malaysia’s Civil Aviation Authority and the office of Najib Razak, the Malaysian prime minister, to confirm the communications record. Only the prime minister’s office responded, saying that it would not release this data.

Relatives of Chinese passengers on board MH370 vented their fury on Malaysian officials yesterday in their first meeting in Beijing, denouncing them for time-wasting.

“We wanted to see you in the first 24 and 48 hours, so that we wouldn’t have had to bear the suffering of the last 13 days,” shouted one anguished relative, his voice quivering. Chinese citizens make up 153 of those on board Malaysia Airlines flight 370, two thirds of the total.

•Pieced together from BBC and Telegraph reports. Photo shows rescue workers.

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