BEIJING — A robotic submarine dove into the ocean to look for lost Flight 370 for a third time Wednesday while the head of a British water wreckage recovery firm says he believes searchers have homed in on the location of the plane.
Meanwhile, the families of Chinese passengers who were on the Malaysia Airlines plane that disappeared March 8 lashed out at Malaysian authorities for not telling them what is going on.
"You are all bloody liars and you are lying to us again now," one relative shouted at a teleconference in Beijing with high-level Malaysian government and airline officials in Kuala Lumpur. "You have absolutely no shame."
Off Australia's western coast, the U.S. Navy Bluefin 21 sub surfaced early for the second time in as many missions, this time after experiencing technical difficulties. It was sent back into the water after its data were downloaded but there's been no sign of the plane, according to the search coordinator.
David Mearns, who heads British-based Bluewater Recoveries but is not involved in the search effort, told the Australian Broadcasting Corporation that he believes the sounds picked up days ago by sonar devices are from the data recorders of the missing plane.
He said that would mean the wreckage of the plane is in the general area of the Indian Ocean that searchers are in, and it is just a matter now of locating the wreckage by sight.
"Obviously for the sake of the families and for everybody else they will want photographic proof and that will be coming shortly," Mearns said.
In addition to the underwater Bluefin-21, up to 13 planes and 11 ships continued to search for the plane Thursday, said the Australia-led Joint Agency Coordination Center. The planes and ships will cover a visual search area totaling about 15,580 square miles.
The center of the area lies 1,348 miles northwest of Perth, the agency said. The Bluefin-21 has covered 35 square miles so far, and data analysis from its latest mission is underway, said the agency, which is responsible for the multi-national search and recovery effort. An oil sample found Sunday near the search area has arrived in Perth for detailed testing.
Australian search officials had said they picked up "possible signals" from a man-made source more than a week ago and those signals have now stopped. The Australian air force P-3 Orion, which has been dropping sonar buoys into the water near where the sounds were picked up four times, have not verified the pings as coming from Malaysia Airlines Flight 370.
The two data recorders, also known as black boxes, emit signals via battery-power. But the battery life is roughly 30 days, and the flight vanished March 8.
The Beijing-bound flight from Kuala Lumpur with 239 people aboard disappeared soon after takeoff from the Malaysia capital. In Beijing, many Chinese relatives of the 153 missing Chinese passengers still hope for a miracle.
But they are increasingly aiming anger and demands for information on Malaysian authorities they believe are concealing the truth.
More than 200 relatives gather daily at a meeting room in the Lido Hotel for news updates, regular meetings with Malaysian representatives and occasional prayer sessions. Malaysia Airlines is paying for their accommodation and food, and has offered counseling services.
But at Wednesday's conference tempers boiled over and Chinese family members turned their backs on the screen as a protest and then walked out. Jiang Hui, a representative of the relatives' self-appointed committee, said families are angry that the Malaysian officials have not come to Beijing to address the Chinese relatives in person.
The Malaysian authorities had promised to send a high-level technical team to Beijing every five days, Jiang said, but none had arrived since April 3.
"They failed to meet our normal demands and our requests for communication, it's useless to sit here and keep listening," he said.
"I think today's action will put some pressure on the Malaysian government, it's useful," said Zhang Hongjie, whose wife Zheng Ruixian was on the flight. "I still have hope we will learn the truth, as long as we keep struggling. Nothing is impossible."
Jiang threatened further protests if Malaysian technical officials fail to come for face-to-face talks on a long list of technical issues the relatives have compiled, including detailed questions about the plane's black boxes and emergency locator transmitters.
"If they don't come I will go again to Malaysia, and I will ask their prime minister 'Is this how your government easily tramples on and denies its promises?'" he said. "In the end, what is the truth and the problems they want to cover up?"
The Chinese government has criticized Malaysia's response to the crisis, and several Chinese celebrities have vowed to boycott Malaysia and its goods.
Some of what the relatives demand is to help them cope emotionally with the mystery of the disappearance, such as pleas for Malaysia to release video footage of their loved ones from the plane's departure gate at Kuala Lumpur airport. A video posted online Wednesday by the relatives committee ends with the line, "We hope a miracle could happen, we look forward to seeing you back."
"So many days have passed, I miss my son," said one middle-aged man. "I want to see the last video, so we can know what he wore and what he was like at that time."
There are signs that Chinese authorities are losing patience with the relatives. China's ruling Communist Party has long been nervous of independent groups that organize and protest, however justified their cause. The relatives communicate through social media such as WeChat, and threaten to take their protests to the streets again.
At a meeting Tuesday afternoon at the hotel, one man complained that several relatives had been "visited by some unidentified people, who persuaded us to leave the Lido, waiting at home instead. I told him I won't leave," he said.
"If I leave here, and then want to return, I might be stopped from getting on the train back," he said, expressing a genuine fear in China where local government enforcers routinely stop citizens from traveling to the capital to protest or pursue justice.
Several other relatives shouted that they will not give up until they see their loved ones "come back."
A man from central China's Henan province, whose son was on the flight, said he received several calls from local officials demanding he return home.
"'I won't go back,' I told them, 'because I can get news more quickly here,'" he said.
The family members asked that their names not be used out of fear of what Communist Party authorities will do to them for complaining. The relatives have not yet directed their anger at Chinese authorities but their attempts to involve China's top leaders are already sparking tension.
Most relatives signed and marked red fingerprints on a two-page letter seeking assistance from Premier Li Keqiang. The man who collected the signatures was later confronted by a government official outside the hotel.
"It's not right for you to do this," said the official, as they quarreled fiercely.
"Why not?" argued the relative. "A journalist asked to read it, I refused her, we just want our country's leaders to help us," he said.
The waiting and conflicts are too much for some people.
"It's torture for me and all relatives here," said Zhang Hongjie. "Many relatives, especially the old, went to consult doctors. They have various problems such as insomnia, pains everywhere, mental and physical problems."
Liu Jiang, a doctor from China's emergency ambulance service who is treating the family members in Beijing, said many of the families simply cannot accept that their loves ones are dead.
"Some relatives have asked for psychological help, but not all relatives are in a bad way emotionally," he said.
Wreckage recovery operator Mearns, who found the HMAS Sydney more than 60 years after it sank in the Indian Ocean in 2008, said he believes the families will have the answer to the fate of their loved ones but that it will take time.
"We do these searches in a grid pattern and it's very much like we call it mowing the lawn," Mearns told the Australian Broadcasting Corporation. "So when you mow your lawn you make very straight lines and the next line you overlap to make sure you're leaving no holidays."
Contributing: Sunny Yang. Bacon reported in McLean, Va.