April 8, 2014 -- Updated 0522 GMT (1322 HKT)
(CNN) -- The underwater pulses that an Australian navy ship detected over the weekend have not been heard since -- but authorities are not letting that deter them in the search for missing Malaysia Airlines Flight 370.
"We have at least several days of intense actions ahead of us," Australian Defense Minister David Johnston told reporters Tuesday. "We're throwing everything at this difficult, complex task."
Investigators hope the signals could be locator beacons from the plane's data recorders, but they're not sure yet.
But buoyed by the hope that they're closing in, they reduced the size of the search area Tuesday.
Now, they are focusing on a smaller area in the Indian Ocean: 30,000 square miles (77,580 square kilometers) about 1,400 miles (2,270 kilometers) northwest of Perth. That's about a third of the size of the previous search zone.
"Instead of looking at an area the size of Texas, we're now looking in an area the size of Houston,"
aviation expert Geoffrey Thomas told CNN.
Time, however, is running out.
The batteries powering the beacons, which are designed to start sending signals when a plane crashes into water, last about 30 days after the devices are activated.
Experts have said it's possible that the batteries could last several days longer if they were at their full strength.
"We need to continue ... for several days right up to when the point at which there's absolutely no doubt that the pinger batteries will have expired,"
said retired Air Chief Marshal Angus Houston, the chief of the Australian agency coordinating the search.
Retired Royal Air Force Lt. Col. Michael Kay said he sees the hunt for the pingers going another week and a half.
"We know that the batteries can last up to 40 days," Kay told CNN.
"If I was Angus Houston, I would be putting the search out to at least 42, 43 (days) to make absolutely sure that the batteries had failed."
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