Officials revise last words from cockpit

• NEW: Flight Lt. Russell Adams had described the objects as the "most promising leads"


• NEW: A conclusive piece of debris is needed to narrow down the search area


• NEW: Search crews are in a race against time to find data, voice recorders


• It's the most vessels to comb the search area so far

Kuala Lumpur, Malaysia (CNN) -- Potential leads on the missing Malaysian jetliner keep coming. So do the setbacks and frustrations.

Four orange objects spotted by aircraft searching for the plane in the treacherous Indian Ocean turned out to be fishing equipment, Australian officials said Monday.

Flight Lt. Russell Adams had described the objects found Sunday as the "most promising leads."

But on further analysis, they turned out to be fishing equipment, once again dashing hopes of finding the jetliner that vanished March 8.

"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."

Search crews from various nations have found an array of potential leads, only to later shoot down any links to the missing plane. They've included dead jelly fish and other garbage floating in the southern Indian Ocean.

Race against time

With every passing minute, it becomes harder to find the flight data recorders and cockpit voice recorders. Batteries on the "pinger" -- the beacon that sends a signal from recorders -- are designed to last about 30 days.

Malaysia Airlines Flight 370 disappeared 23 days ago en route from Kuala Lumpur to Beijing.

An Australian ship fitted with a U.S. ping detector is set to join the search Monday in a desperate race against time.

The focus is on helping find the flight recorders. Find the pinger and you find the recorders. Find the recorders, experts say, and you are steps closer to solving the mystery of Flight 370. Flight data recorders capture a wide array of information, including altitudes, air speeds and engine temperatures.

Crews loaded an American pinger locator and undersea search equipment onto the Ocean Shield, an offshore support vessel of the Australian navy. The ship was originally set to depart Monday morning, but authorities said it would be delayed by several hours for an inspection.

It will take the ship up to three days to reach the search area.

But that's just one of the many hurdles.

'Conclusive piece of debris'

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 they deploy 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 search intensified Monday with 10 aircraft and 10 ships combing the area 1,150 miles (1,850 kilometers) west of Perth. It's the most vessels to comb the search area so far.

If located, the black box could provide crucial insight into what caused the aircraft to vanish with 239 people aboard en route from Kuala Lumpur to Beijing.

'Search increasing'

Abbott said he wouldn't set a time frame on the search for the missing plane.

"We can keep searching for quite some time to come. We will keep searching for quite some time to come. ... The intensity of our search and the magnitude of our operations is increasing, not decreasing," he said.

And so is frustration among relatives of those aboard the doomed flight.

Relatives' demands

Dozens of Chinese family members of those aboard the flight visited a Kuala Lumpur temple Monday. 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 for announcing on March 24 that the plane had crashed even though there was no "direct evidence."

Of the 239 people aboard the jetliner, 154 were Chinese.

Family members have accused Malaysian officials of giving them confusing, conflicting information since the plane vanished more than three weeks ago.

Last week, relatives were told everyone aboard had died. But Hishammuddin Hussein, Malaysia's acting transportation minister, told reporters Saturday he had not closed the door on the hope that there could be survivors.

Beijing has also publicly slammed Malaysia's efforts to find the Boeing 777. But Malaysia says it's done its best with what it has.

"History will judge us as a country that has been very responsible," said Hishammuddin Hussein, Malaysia's acting transport minister.

Data analysis

The latest data analysis shows the plane ended up in the southern Indian Ocean.

Data recorders are built to withstand the rigors of flight and the trauma of crashes.

The pinger locator can detect flight recorders on downed aircraft to a maximum depth of 20,000 feet. The autonomous underwater vehicle has side-scanning sonar that is useful in a debris field with underwater objects, Rear Adm. John Kirby said.

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.

Similar technology was used successfully in the hunt for Air France Flight 447, which disappeared in June 2009.

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.