Australia: No More 'Pings' Heard in MH370 Search
A relative of Chinese passengers aboard Flight MH370 takes a nap against the wall displaying messages of wishes for the passengers during a briefing held by Malaysia officials at a hotel in Beijing, April 11, 2014.
A woman, the daughter of a Chinese passenger on Flight MH370 shows her mobile phone displaying a photo of her father near the wall displaying messages of wishes for the passengers at a hotel in Beijing, April 11, 2014.
A woman ties a message card for passengers onboard the missing Malaysia Airlines Flight 370 at a shopping mall in Petaling Jaya, near Kuala Lumpur, Malaysia, April 10, 2014.
Spectators take photos of a Chinese Ilyushin IL-76 aircraft as it comes in for a landing at Perth International Airport after returning from the ongoing search operations for missing Malaysia Airlines Flight 370, Perth, Australia, April 10, 2014.
A man places a candle on top of a white board set up to place messages for passengers on Flight MH370 during a candlelight vigil in Kuala Lumpur, April 6, 2014.
People place candles on a banner reading, "Pray for MH370" after a special prayer for passengers onboard the missing plane at the Malaysian Chinese Association headquarters in Kuala Lumpur, April 6, 2014.
A U.S. Navy towed pinger locator is pictured on a dock at HMAS Stirling naval base near Perth.
Chinese patrol ship Haixun 01 is pictured during a search for Flight MH370, in the south Indian Ocean, April 5, 2014. (CNS photo)
The Bluefin 21, an Artemis autonomous underwater vehicle, is hoisted back on board the Australian Defence Vessel Ocean Shield after a successful buoyancy test in the southern Indian Ocean, April 4, 2014.
A flight lieutenant monitors a TAC station onboard a Royal New Zealand Air Force P3 Orion during search operations for Flight MH370 in the southern Indian Ocean, April 4, 2014.
The Search for Flight MH370
Search crews in the southern Indian Ocean are urgently trying to relocate electronic transmissions they believe came from the missing Malaysian airliner's black box.
No signals have been heard since Sunday, when U.S. Navy equipment detected two distinct sounds consistent with acoustic pings from the plane's flight data and cockpit voice recorders.
Australian search chief Angus Houston said at a news conference Tuesday that without more pings, authorities are unable to deploy a robot to search the ocean floor for wreckage.
"If we go down there now and do the visual search it will take many, many, many days because it's very slow, very painstaking work to scour the ocean floor. And of course the depths are very deep and it's very challenging,” said Houston.
Houston said the search for underwater signals will likely take "several days."
Authorities are running out of time, since the batteries on the black box's locator beacon are built to last for around 30 days. The plane disappeared one month ago Tuesday.
Up to 14 planes and 14 ships face favorable weather conditions Tuesday as they continue the search in an 80,000-square-kilometer area northwest of the Australian city of Perth.
The ocean there has an average depth of about 4.5 kilometers, making it extremely difficult for authorities to find any debris or locate the black box's faint electronic signals.
Officials have said it is increasingly unlikely that any wreckage will be found on the surface of the water because of natural ocean drift and recently stormy seas.
Chinese relatives of the missing passengers gathered in Beijing late Tuesday for a candlelight vigil to mark the one-month anniversary. Steve Wong, a spokesman for the families, said they will not give up hope until wreckage is found.
"It is not the time for memorial ceremonies yet. We need to persist in resolving this situation, to persist in finding the clues of what really happened and finding our relatives. This is the argument that we have been persistently raising since the first day and will continue to do it in the future," said Wong.
The families are upset at what they feel is a lack of transparency by Malaysian authorities, as well as several false leads in the search for the plane.
The Boeing disappeared early on March 8 with 239 people aboard on a flight from Kuala Lumpur to Beijing.
The plane vanished without any distress calls, and authorities have refused to rule out any possibilities, including hijacking, sabotage or a mechanical malfunction.
Malaysian officials say they are continuing to investigate whether any deliberate action by the pilots or crew could have sent the plane down.