PERTH, Australia >> As a robotic submarine dived into the ocean to look for lost Flight 370, angry Chinese relatives stormed out of a teleconference meeting Wednesday to protest the Malaysian government for not addressing them in person. 

The 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.

As the search continued, more than 100 relatives of Chinese passengers on the plane walked out of a teleconference meeting with senior Malaysian officials, an act of defiance over a lack of contact with that country’s government and for taking so long to respond to their demands. 

The family members had gathered in a meeting room at a Beijing hotel where Malaysia Airlines had provided lodging and food. But they stood and filed out shortly before the call with Malaysia’s civil aviation chief, Azharuddin Abdul Rahman, and others as it was about to start.

"These video conference meetings often don’t work, the sound stops and it’s constantly disrupted. Is that how we are going to communicate?" said Jiang Hui, one of the family members, after the walkout. "Do they need to waste our time in such a way?"

Jiang said the Malaysian government had not met demands the relatives had presented to them weeks ago in Malaysia — an apology for the way they’ve handled the matter along with meetings with the Malaysian government and airline officials. They also have requested to sit down with executives from Boeing and Rolls-Royce, the manufacturer of the plane and its engines.

The Boeing 777 vanished March 8 with 239 people on board while en route from Kuala Lumpur, Malaysia to Beijing. Radar and satellite data show it flew far off-course for an unknown reason and would have run out of fuel over the southern Indian Ocean west of Australia. 

A ship-towed device detected four signals underwater that are believed to have come from the airliner’s black boxes shortly before the beacons’ batteries died. The sounds helped narrow the search area to the waters where the Bluefin 21 is now operating.

The U.S. Navy’s unmanned sub cut short its first mission on Monday because it exceeded its maximum operating depth of 4,500 meters (15,000 feet). Searchers moved it away from the deepest waters before redeploying the sub to scan the seabed with sonar to map a potential debris field.

On the ocean surface, up to 14 planes and 11 ships were searching a 62,000-square-kilometer (24,000-square-mile) patch of sea about 2,200 kilometers (1,400 miles) northwest of Perth on Wednesday. The surface search is expected to end soon as not a single piece of debris connected to the plane has been found.

Investigators are also waiting on test results from an oil slick found about 5,500 meters (3.4 miles) from where the underwater sounds were detected. 

In addition to finding the plane itself, investigators want to recover the black boxes in hopes the cockpit voice and flight data recorders contain answers to why the plane lost communications and flew so far off-course before disappearing.

Associated Press writers Kristen Gelineau in Sydney, Rod McGuirk in Canberra, Australia and videojournalist Aritz Parra in Beijing, contributed to this report. 

Follow Margie Mason on Twitter at twitter.com/MargieMasonAP