The sea bed search for the missing Malaysia Airlines jet is poised to widen as a sonar scan of the most likely crash site deep beneath the Indian Ocean nears completion without yielding a single clue.
Meanwhile in Beijing, about 50 relatives of Chinese passengers on the Boeing 777 continued a sit-in protest outside the Malaysian embassy after officials failed to show up to update them on the search.
The Australian search co-ordination center said a robotic submarine had scanned 95% of a 120-square-mile search area since last week but had found nothing of interest. The US Navy's Bluefin 21 is creating a three-dimensional sonar map of the ocean floor near where signals consistent with aircraft black boxes were heard on April 8.
The search area is a circle with a six-mile radius,2.8 miles deep off the west Australian coast. The search of the target area is due to be completed within days.
"If no contacts of interest are made, Bluefin 21 will continue to examine the areas adjacent to the 10-kilometre radius," the centre said.
"We are currently consulting very closely with our international partners on the best way to continue the search into the future," it added, referring to Malaysia, the United States and China.
Malaysia hopes to release to the public a preliminary investigation report on the plane's disappearance next week, Malaysian prime minister Najib Razak's department said.
"We are also looking at releasing the cargo manifest and aircraft seating arrangement," said an official.
The report has already been sent to the United Nations' International Civil Aviation Organisation.
The Malaysian government, which has primary responsibility for the investigation, has been criticised for mismanaging the search, concealing information about the tragedy and of being too slow to update families of the missing on developments.
In Beijing, the relatives had marched to the Malaysian embassy from their hotel after Malaysian officials failed to arrive for a promised briefing.
"We keep on waiting because we want the news," said Steve Wang, whose parents were aboard the flight and who has served as a representative for the relatives.
"What we are concerned about is where is the plane, and where are our loved ones."
Some relatives scuffled with police who tried to prevent them leaving the hotel. Today, more than 100 police and paramilitary officers had cordoned off the area around the embassy in a north-eastern diplomatic district that is also home to the US embassy.
Mr Wang said the relatives felt slighted by the failure of the Malaysian officials to appear for the briefing. A number of Chinese relatives have refused to accept the theory that the plane crashed in the Indian Ocean and insist that Malaysian officials have not told them the truth about the plane's disappearance.
Australian defence minister David Johnston said an announcement was likely next week on the next phase of the search for the jet which vanished with 239 passengers and crew - mostly Chinese - on board on March 8 during a flight from Kuala Lumpur to Beijing.
He said the next phase was likely to deploy more powerful side-scan sonar equipment that can delve deeper than the Bluefin 21.
Up to eight planes and 10 ships are searching for debris over a 19,000 square mile ocean expanse 1,000 miles north west of the city of Perth where the search is headquartered.