By Faith Karimi and KJ Kwon
KUALA LUMPUR, Malaysia (CNN) — Potential leads on the missing Malaysia Airlines Flight 370 keep coming. So do the setbacks and frustrations.
Monday’s search ended without finding anything significant, Australian officials said. Four orange objects spotted by search aircraft and earlier described as promising turned out be nothing more than old fishing gear, they said.
Underscoring the difficulty of the search, U.S. Navy officials loaded underwater locating gear aboard an Australian naval support vessel and set out to sea Monday evening, but won’t be able to make use of the equipment until searchers narrow the search zone.
U.S. Navy Cmdr. William Marks told CNN’s “State of the Union” that his team needs a conclusive piece of debris to narrow down the search area before deploying the equipment.
“We have to be careful not to send it in the wrong place,” he said. “But we also wanted to get it out there as close as we can to what we believe is the right place.”
The gear includes a pinger locator that’s towed behind a ship and scans for the sound of the locator beacon attached to the plane’s flight data recorder. Also on board is a remotely operated submersible that can look for wreckage on the ocean floor.
It will take the ship, the Ocean Shield, three days just to get to the search zone, leaving precious little time to locate the plane’s flight data recorders before the batteries on its locator beacon run out. The batteries are designed to last 30 days; the plane has been missing 23 days.
Under favorable sea conditions, the pingers can be heard 2 nautical miles away. But high seas, background noise, wreckage or silt can all make pingers harder to detect.
In this case, searchers barely know where to look at all.
“We are searching a vast area of ocean, and we are working on quite limited information,” Australian Prime Minister Tony Abbott told reporters Monday. “Nevertheless, the best brains in the world are applying themselves to this task. … If this mystery is solvable, we will solve it.”
And he vowed to keep looking.
“The intensity of our search and the magnitude of our operations is increasing, not decreasing,” he said.
Ten aircraft and 11 ships scouted more than 98,000 square miles (254,000 square kilometers) of Indian Ocean on Monday looking for the missing plane, Malaysia’s acting Transportation Minister Hishammuddin Hussein said Monday.
Flight 370 vanished March 8 while flying from Kuala Lumpur to Beijing.
A new Australian Joint Agency Coordination Center is being formed to synchronize search efforts among Australian agencies and other countries taking part in the search, Hishammuddin said.
And Malaysia will ask the United States about the possibility of deploying more military assets, he said.
New details on handoff
On Monday, Malaysia’s Transport Ministry said the final voice transmission from the cockpit of Flight 370 was “Good night Malaysian three seven zero.”
That’s a departure from earlier language in which Malaysian authorities said the final transmission was “All right, goodnight.”
The new language is routine and is not a sign of anything untoward occurring aboard the flight, said CNN aviation analyst Mary Schiavo.
But she said it does raise questions about how Malaysian officials have handled the investigation.
“Well, it speaks to credibility issues, unfortunately,” she said.
Family members of people on board Flight 370 have accused Malaysian officials of giving them confusing, conflicting information since the plane vanished more than three weeks ago.
On Monday, dozens of Chinese family members visited a Kuala Lumpur temple. They chanted, lit candles and meditated.
“Chinese are kindhearted people,” said Jiang Hui, the families’ designated representative. “But we can clearly distinguish between the good and evil. We will never forgive for covering the truth from us and the criminal who delayed the rescue mission.”
Jiang asked Malaysia to apologize for announcing March 24 that the plane had crashed, despite the lack of any “direct evidence.”
At the daily press briefing, Hishammuddin responded, saying Malaysian Prime Minister Najib Razak had not used the word “crash” or mentioned a lack of survivors in his announcement that the plane’s flight had “ended” in the southern Indian Ocean.
And, he said, Malaysian authorities were not hiding anything by declining to release some details of the missing flight. Some details are part of ongoing investigations into what happened to the plane, he said.
“We are not hiding anything. We are just following the procedure that is being set.” he said.
He described a meeting Saturday between Malaysian authorities and Flight 370 relatives as “the most difficult meeting I’ve ever attended.”
“The families are heartbroken. For many, the strain of the past few weeks has been unbearable,” he said.
He said Malaysia will hold a high-level briefing for families where experts will explain some of the data and methodology used to guide the search.
He also said authorities have discussed with the families what happens if they are unable to find debris from the missing plane. But he declined to discuss it with reporters Monday, saying “to be fair to the families, that is something I would not want to share with the public at the moment.”
Beijing has also publicly slammed Malaysia’s efforts to find the Boeing 777. Of the 239 people aboard the jetliner, 154 were Chinese. But Malaysia says it’s done its best with what it has.
“History will judge us as a country that has been very responsible,” Hishammuddin said.
CNN’s Dana Ford, Mitra Mobasherat, Kyung Lah, Yuli Yang and Paula Hancocks contributed to this report. KJ Kwon reported from Kuala Lumpur; and Faith Karimi wrote from Atlanta.
™ & © 2014 Cable News Network, Inc., a Time Warner Company. All rights reserved.