BEIJING (AFP) - A Chinese ship involved in the Indian Ocean search for flight MH370 detected a "pulse signal" at a frequency used by aircraft black boxes on Saturday, but Australia warned there was no evidence yet that it was linked to the missing plane.
China's Xinhua news agency said the signal picked up by a black box detector on the vessel Haixun 01 had a frequency of 37.5kHz - identical to the emergency beacon signal emitted by flight recorders.
Chinese television reporters aboard the ship said crews had briefly detected a similar signal on Friday, but said it was yet to be established whether the sonic pings were from MH370's black box, whose roughly 30-day locator signal is due to expire soon.
The Malaysia Airlines Boeing 777 vanished March 8 en route from Kuala Lumpur to Beijing, triggering an unprecedented international search across huge expanses of first the South China Sea and now the Indian Ocean.
Australia authorities leading the multinational search in seas far off the country's west coast advised caution over Saturday's development.
"The characteristics reported are consistent with the aircraft black box," retired armed forces chief Angus Houston, head of Australia's search coordination centre, said in a statement.
He added that "a number of white objects were also sighted on the surface about 90km from the detection area".
"However, there is no confirmation at this stage that the signals and the objects are related to the missing aircraft," he said.
Australian authorities were seeking more information from the Chinese side and were considering deploying air assets to the detection area, he added.
False hopes, including sightings of suspected debris that turned out to be random flotsam, have repeatedly punctuated the search for the missing plane, keeping the anguished families of the 239 people aboard on an emotional roller-coaster.
"This is not the first time we have had something that has turned out to be very disappointing," Australian Defence Minister David Johnston cautioned on ABC television.
Malaysian authorities also said they were seeking to verify the report before commenting.
Search teams from eight nations, including Australian and British ships with special detection equipment, are racing against time to find the black box and its vital flight data before the signal fades, hoping it will shed light on the MH370 mystery.
The Haixun 01 picked up the pulse signal at about 25 degrees south latitude and 101 degrees east longitude, Xinhua said. That is about 1,500km northwest of Perth.