(Adds India formally telling Malaysia it has found no sign of plane)
* More international planes, ships head to remote search zone
* Malaysian minister concerned suspected debris may be unidentifiable
* India formally tells Malaysia no sign of plane crossing its territory, sources say
By Michael Martina and Matt Siegel
KUALA LUMPUR/PERTH, Australia, March 22 (Reuters) - Two weeks after a Malaysian airliner carrying 239 people vanished, international teams stepped up their search deep in the southern Indian Ocean on Saturday, as a Malaysian minister expressed fear a possible sighting of debris may be another false lead.
Searches by more than two dozen countries have turned up little but frustration and fresh questions about Malaysia Airlines Flight MH370 which disappeared on a scheduled flight from Kuala Lumpur to Beijing on March 8.
Six aircraft and two merchant ships were scouring an area of the remote southern Indian Ocean where suspected debris was spotted by satellite six days ago.
There were no reports of any wreckage being found.
Australia, which announced the satellite image and is coordinating the rescue, has cautioned the objects might be a lost shipping container or other debris and may have since sunk.
"Even though this is not a definite lead, it is probably more solid than any other lead around the world and that is why so much effort and interest is being put into this search," Deputy Prime Minister Warren Truss told reporters.
According to several people familiar with the matter, India has told Malaysian investigators that it had found no evidence the plane flew through its airspace, making the satellite debris lead more solid.
It was the first formal notification that India had come up empty-handed after checking its radar records, the sources said.
China, Japan and India were sending more planes and Australian and Chinese navy vessels were also steaming towards the southern zone, more than 2,000 km (1,200 miles) southwest of Perth.
Weather conditions were good, with 10 km (6 miles) of visibility, according to officials - a crucial boost for a search that is relying more on human eyes than the technical wizardry of the most advanced aircraft in the world.
"I AM NOT GOING TO GIVE UP"
Malaysian Defence Minister Hishammuddin Hussein said on Friday searchers realised that time was running out. The "black box" voice and data recorder only transmits an electronic signal for about 30 days before its battery dies.
"I am still quite concerned that - it's been two days - and yet the searches have not come out with any debris," he said on Saturday about the operation in the southern Indian Ocean.
"I am not going to give up... My biggest concern is that we are not able to identify the debris, having to go back to the two corridors."
Aircraft and ships have also renewed the search in the Andaman Sea between India and Thailand, going over areas in the northern corridor that have already been exhaustively swept to find some clue to unlock one of the biggest mysteries in modern aviation.
The Pentagon said it was considering a request from Malaysia for sonar equipment. The P-8 and P-3 spy planes, which the United States is already deploying in the search, also carry "sonobuoys" that are dropped into the sea and use sonar signals to search the waters below.
Investigators suspect the Boeing 777 was deliberately diverted thousands of miles from its scheduled path. They say they are focusing on hijacking or sabotage but have not ruled out technical problems.
Britain's Daily Telegraph published what it said was a transcript of communications between the cockpit of Flight MH370 and Malaysian air control, but few if any new clues emerged.
The search itself has strained ties between China and Malaysia, with Beijing repeatedly leaning on the Southeast Asian nation to step up its hunt and do a better job at looking after the relatives of the Chinese passengers.
For families of the passengers, the process has proved to be an emotionally wrenching battle to elicit information.
In a statement on Saturday, relatives in Beijing lambasted a Malaysian delegation for "concealing the truth" and "making fools" out of the families after they said they left a meeting without answering all their questions.
"This kind of conduct neglects the lives of all the passengers, shows contempt for all their families, and even more, tramples on the dignity of Chinese people and the Chinese government," they said.
Some experts have argued that the reluctance to share sensitive radar data and capabilities in a region fraught with suspicion amid China's military rise and territorial disputes may have hampered the search. (Additional reporting by Ruairidh Villar, Tim Hepher, Niki Koswanage, A. Ananthalakshmi and Siva Govindasamy in Kuala Kumpur, Lincoln Feast in Sydney and Jason Lee in Beijing; Editing by Michael Perry and Nick Macfie)