Chinese state media reports that a ship has detected a pulse signal in the MH370 search zone in the southern Indian Ocean. (Reuters)

A Chinese naval ship searching for the missing Malaysian airliner has picked up an audio pulse in the Indian Ocean at the same frequency emitted by the plane’s emergency locator beacons, Chinese media reported Saturday, but it has not been established whether the signal is connected to the plane.

The head of the multinational search, retired Air Chief Marshal Angus Houston, stressed on Sunday that the pulses are “an important and encouraging lead,” but he cautioned against any conclusions until the signals can be verified.

Houston also told media at a briefing in Perth, Australia, that an Australian vessel, the Ocean Shield, is investigating a separate acoustic detection.

The news injected some hope into the search efforts, coming at the time when the batteries on those location beacons could expire at any moment.

China’s state-run Xinhua News Agency, which has a reporter aboard the Haixun 01 ship, reported that a black box locator heard the signal Saturday at around 25 degrees south latitude and 101 degrees east longitude — broadly in the same area where the search effort has been concentrated in recent weeks, in the Indian Ocean about 1,000 miles northwest of the Australian city of Perth.

The signal was measured at a frequency of 37.5 kilohertz and was repeating at one-second intervals, Xinhua reported.

Anish Patel, president of Florida-based pinger manufacturer Dukane Seacom, told CNN that was the correct frequency for the two emergency locator beacons that are built into the plane’s black box flight data recorder and its cockpit voice recorder. He added that it was not a frequency that “readily occurs in nature.”

“The reason it was chosen was to give that standout quality that does not get interfered with by the background noise that readily occurs in the ocean,” he said.

Still, Patel said that the news should be treated with skepticism until it can be corroborated, and that the ship should have picked up two signals from the two beacons, if they are still close to each other and weren’t damaged by the crash.

“There could be a host of reasons they are not picking up two signals, but that is one of the initial questions I’d ask — we should be picking up two signals.”

A crew member aboard the Haixun 01 told China’s Xinmin Evening News newspaper that the pulse was consistent with a sample they had been given by Boeing, the missing plane’s manufacturer.

China Central Television reported that crew members had first heard the signal Friday, but for only 10 minutes, and that they had not been able to record it during that time. The ship searched the same area for five hours Saturday without any luck before hearing the signal again for around 90 seconds, around two nautical miles away from the first location, CCTV reported.

What happened to Flight 370?

David Gallo of the Woods Hole Oceanographic Institution said the location where the signal was heard is close to an undersea feature called the East Indiaman Ridge, named after sailing ships of the British East India Company. He added that the average depth of the ocean there was about 13,000 feet.

If the signal is shown to have come from the plane, it should be feasible to locate the plane on the ocean floor in that area, he said, given the right team, with the right technology, and given time and luck.

“There’s nothing unusual about the seafloor in the area of interest, and working this type of terrain at that depth is routine for ocean scientists,” he said. “That doesn’t mean it’s easy.”

Aviation expert Richard Aboulafia of the Teal Group in Fairfax, Va., called it “potentially good news” but warned that, even if the flight data recorder and cockpit voice recorder are found, they might not contain all the information needed to unravel the mystery. The cockpit recorder, for example, keeps only the last two hours of audio, which “could be two hours of silence,” he said.

An Australian and a British ship began listening for the pings from the locator beacons on Friday and will soon be joined by a British nuclear submarine with sonar capabilities.

Up to 10 military planes, three civilian jets and nine other ships took part in the search Saturday, in an 88,000-square-mile patch of ocean more than 1,000 miles northwest of Perth, the Australian agency coordinating the search said.

The head of that agency, Australian Air Chief Marshal Angus Houston, acknowledged that the search area was essentially a best guess and noted that the time when the plane’s locator beacons would shut down was “getting pretty close,” the Associated Press reported.

Xu Yangjingjing contributed to this report.