Australian searchers have relocated an underwater electronic signal that could be from the missing Malaysian jetliner in the Indian Ocean, the search coordinator says, allowing them to narrow the focus of their effort to find wreckage.

Angus Houston, who is leading the joint search, said in Perth on Wednesday that equipment aboard the Australian ship Ocean Shield twice reacquired signals first detected last week that could be coming from the black box data and voice recorders on board the missing Malaysian Airlines Flight 370.

He said the ship has now heard the signal, which is "not of natural origin," a total of four times, most recently a seven-minute transmission Tuesday night.

The new data has allowed searchers to further reduce the size of the search area, Houston said.

"I believe we are searching in the right area'' for the wreckage, he said. He hopes more transmissions will be detected and, "in a matter of days we will be able to find something on the bottom that might confirm that this was the last resting place of MH370."

Houston cautioned that nothing can be confirmed until wreckage from the plane is visually identified.

Searchers are in a race against time, trying to gain as much information from the underwater signals as they can before the onboard batteries -- already past their expected lifespan -- expire and the data recorder pingers go silent.

It's been 33 days since the plane was lost on a flight from Kuala Lumpur to Beijing, and Houston noted that the expected time life of the batteries on the black box pingers is 30 days.

"It is important that we gather as much information .... while the pingers are still transmitting,'' he said.

"The last signal we got was a very weak signal,'' he said.

Before Wednesday's report by Houston, search crews had last heard the signals early Sunday. The trouble relocating the signals had reduced confidence that the wreckage would be located anytime soon.

Peter Goelz, a former managing director of the National Transportation Safety Board, told USA TODAY the inability to reacquire the signal was a "setback."

"I think we could be talking about months if not years of searching," Goelz said.

During a press conference Tuesday in Perth, Australia, Minister of Defense David Johnston said crews were prepared to deploy a small submersible vessel as soon as they receive another ping transmission. The black box's ping batteries, however, are reaching their limit.

"I think they (authorities) have to continue with the pinger search for another week or 10 days," Goelz said. "After that, they have to reassess how they will search and who will pay for it."

The underwater vehicle, the Bluefin 21 unmanned sub, is loaded with equipment that can create a sonar map of an area to chart any debris on the sea floor. But it works slowly, so the search area must be sharply trimmed first. Authorities have narrowed the search, but it remains focused on an area nearly 30,000 square miles in size while more clues are sought.

The cost of the effort rises each day. Estimates compiled by Reuters show that Australia, China, the United States and Vietnam have already spent at least $44 million on the deployment of military ships and aircraft.

The news service said the total does not include the aid from countries including Britain, France, New Zealand and South Korea, or numerous other costs such as civilian aircraft, accommodation for hundreds of personnel and expenses for intelligence analysts.

The pinger locator is designed to detect signals at a range of 1 mile, meaning it would need to be almost on top of the black boxes to detect them if they were on the ocean floor.

The Ocean Shield is continuing to comb the ocean, trying to find the signal again.

Additionally, a Chinese search vessel, Haixun 01, also said it briefly heard signals over the weekend. Those signals, more than 300 miles from the other signals, were being investigated by a British naval vessel, HMS Echo, which also has sophisticated listening technology.