A pinger locator sits on an Australian ship in the southern Indian Ocean during the search for the black box of the missing Malaysian Airlines flight MH370. Photograph: Reuters
A Chinese ship has detected an electronic pulse close to where the missing Malaysian Airlines plane is believed to have crashed into the southern Indian Ocean, state media announced late on Saturday.
“Chinese patrol ship Haixun 01 searching for flight MH370 discovered a pulse signal with a frequency of 37.5kHz per second in south Indian Ocean waters,” the official news agency Xinhua reported, as the search entered its fifth week.
It said the pulse was detected by Haixun’s black box detector at around 25 degrees south latitude and 101 degrees east longitude, within the 217,000 sq km search zone.
But Xinhua, which has a reporter on board the vessel, subsequently quoted the China Maritime Search and Rescue Centre as saying the suspected pulse had yet to be confirmed. No wreckage has yet been found in the area despite a massive international hunt.
Meanwhile, Xinhua also said that a Chinese air force plane involved in the search had spotted a number of floating objects in the search area. It was not clear whether these objects were near where the pulse signal was reportedly detected.
The Beijing-bound Boeing 777 disappeared in the early hours of 8 March, shortly after taking off from Kuala Lumpur, with 239 people on board. Investigators have used analysis of the plane’s communication with satellites to identify the search area in the southern Indian Ocean, 1,700km north-west of Perth.
Xinhua’s announcement is the first potentially positive sign in the race against time to find the aircraft’s black box.
Earlier on Saturday Angus Houston, who heads the Australian centre co-ordinating the international operation, warned that searchers were “getting pretty close” to the point at which the electronic beacons on the flight data and cockpit voice recorders would stop emitting signals.
They are certified to send out pulses for 30 days, although experts say they can often last for another 14 days or so.
Anish Patel, the president of Dukane Seacom – which has said it made the beacons for the flight data and cockpit voice recorders on board MH370 – told CNN that the pulse was identical to the standard beacon frequency.
A reporter for Chinese state television said that the signal was heard for around a minute and a half.
David Gallo, who co-led the hunt for Air France flight 447 in the Atlantic Ocean, told the Observer it was not unusual for sound to come and go because numerous factors – such as thermal currents – can have an impact on how it carries.
The Air France search saw a false alarm over a possible signal from the black box, he cautioned. But he added that in this case the frequency of the pulse was unlikely to occur naturally.
“It could very well be one of the beacons,” he said.
Gallo, of the Woods Hole Oceanographic Institute, said that even if towed pinger locators could not detect the precise location of the black box, they might help the search teams narrow it down to an area of 10 sq km or less. The next stage would be to map the sea floor systematically using robots and towed systems, he said.
“When you find [the recorders] there is a sense of satisfaction, but it is also a very sombre moment,” he said.
“It brings the end that the families and loved ones of passengers have been praying and hoping would not come.”
Earlier in the day, Xinhua announced that Chinese search planes had photographed white floating objects in the search zone, but there have already been a string of false alarms in the hunt.
The decision to release the information via Chinese media – rather than the Australian government agency set up specifically to co-ordinate the international operation – is likely to cause friction.
The Joint Agency Co-ordination Centre would not immediately comment on the report.
CNN said an Australian source connected to the search said the centre had learned of the alert several hours earlier but had not been able to communicate directly with Haixun.
While other search crews report possible evidence connected to the flight directly to the joint research centre, the Chinese teams report it to Beijing which then informs the centre, the source added.
It also said an Australian Defence Force spokesman had described the detection of the pulse as “an anomaly of interest”.
Multiple countries are involved in the search, with 13 aircraft, 11 ships and the British nuclear submarine HMS Tireless scouring the search zone on Saturday.
More than 150 of those on board the flight were Chinese nationals. China has contributed several ships and vessels to the search.
Earlier, Hishammuddin Hussein, Malaysia’s defence minister and acting transport minister, told a briefing in Kuala Lumpur that the expense of the search was immaterial compared with the importance of establishing what happened for the relatives of those on board.
“I can only speak for Malaysia, and Malaysia will not stop looking for MH370,” he said.
Hishammuddin announced that an independent investigator would be appointed to oversee three teams pursuing the main lines of inquiry: the plane’s airworthiness, including its maintenance, structures and systems; operational issues, such as flight recorders and meteorology; and medical and human factors.
Investigators believe it was deliberately diverted from its course, but experts say that without the flight data and cockpit voice recorders there is little hope of establishing who was responsible and why. Even then, they caution that the information may not shed much light on the mystery. Cockpit voice recorders hold audio from only the last two hours of the flight and the critical events in this case are likely to have occurred much earlier.