KUALA LUMPUR (AFP) - An interim report into missing flight MH370 said on Sunday that the battery on its underwater locator beacon had expired a year before, but found no red flags relating to the crew or aircraft to shed light on the cause of the disappearance.
An international team of investigators probed the captain and co-pilot's personal, psychological, and financial profiles, and also looked into the backgrounds of the 10 cabin crew.
Their lengthy report, released on the first anniversary of the disappearance, mentioned no findings that cast suspicion on them.
"There were no behavioural signs of social isolation, change in habits or interest, self-neglect, drug or alcohol abuse of the Captain, First Officer and the Cabin Crew," said the report.
The report said that civilian radar had tracked the plane for a short time after it diverted on March 8 of last year, apparently contradicting earlier Malaysian statements that only its military radar had monitored the plane.
The report also found that the battery powering the underwater locator beacon on the plane's flight data recorder was due to expire in December 2012. However, the battery on the plane's cockpit voice recorder was replaced and functioning.
It noted that while batteries can still operate past their official expiry, they may lose effectiveness, calling it an "oversight".
The report said airline blamed a problem in computer systems that track equipment updates, and that it had subsequently carried out a fleet-wide inspection to make sure records were accurate.
Representatives from neither Malaysia's civil aviation authority nor the national carrier were immediately available for comment.
"My major worry is that (search vessels) may have gone over the aircraft but not heard the pings because of this," said Mr Gerry Soejatman, a Jakarta-based aviation consultant, said of the expired battery and the so-far-fruitless search for the jet.
Otherwise, he said the report mostly restated what is already known about MH370.
"There is nothing much to go on with the new report," said Mr Soejataman. "This is because there is little to analyse."
The investigative team was set up in the weeks after the plane's disappearance under International Civil Aviation Organisation (ICAO) requirements and was required to submit its findings within one year of the disappearance.
The report also ticked through a number of the plane's mechanical systems and noted in each case that according to available data and maintenance records, nothing alarming was seen.
Its report is considered only an "interim" one due to the lack of hard evidence.
Suspicion had fallen on the cockpit crew of pilot Zaharie Ahmad Shah and his co-pilot Fariq Abdul Hamid. Other theories have included a mechanical problem or hijack.
The report was focused on air-safety issues related to MH370 and the investigators did not probe the 227 passengers or the possibility of a hijack.
The report stressed that the investigation was ongoing and that "new information that may become available may alter this information".
"The investigation team expects that further factual information will be available from the wreckage and flight recorders if the aircraft is found," it said.
A year-long, Australia-led search effort in the southern Indian Ocean where the Malaysia Airlines Boeing 777 is believed to have crashed has so far yielded no sign of the plane.
Investigators still lack any trace of the jet, including the "black box" data recorders considered most likely to yield clues.
More than 40 per cent of a designated 60,000 sq km zone believed to be the most likely location of the crash site has been scanned for wreckage using sophisticated sonar, but nothing related to MH370 has been found.
Malaysia's Prime Minister said on Sunday his nation remained committed to the so-far fruitless hunt for flight MH370 exactly one year after it went missing, and was hopeful the plane would be found.
"Together with our international partners, we have followed the little evidence that exists. Malaysia remains committed to the search, and hopeful that MH370 will be found," Najib Razak said in a statement to mark the anniversary of the plane's disappearance.
"No words can describe the pain the families of those on board are going through," Najib said, calling the plane's disappearance "without precedent".
"The lack of answers and definitive proof - such as aircraft wreckage - has made this more difficult to bear."
Malaysia's Transport Minister Liow Tiong Lai told AFP in an interview on Saturday that the hunt for MH370 would be sent "back to the drawing board" if the current search zone comes up empty.
He said that meant satellite and other data used to determine the suspected crash region would have to be re-examined, but he would not specify what could happen next.
Many next of kin were deeply critical of Malaysia's initial response to the crisis, saying that opportunities to intercept or track the plane were lost.