A Chinese ship that is part of the multinational search effort looking for the missing Malaysia Airlines plane has detected a "pulse signal" in southern Indian Ocean waters, China's official news agency reported.
The report said a black box detector deployed by the vessel, Haixun 01, picked up a signal at 37.5Hz per second on Saturday at around 25 degrees south latitude and 101 degrees east longitude, according to the Associated Press news agency.
The report said it was not established whether that the signal was related to the missing jet.
Malaysia's civil aviation chief, Azharuddin Abdul Rahman, confirmed that the frequency emitted by Flight 370's black boxes were 37.5 kilohertz and said authorities were verifying the report.
The Australian government agency coordinating the search said the electronic pulse signals are consistent with those of an aircraft black box.
However, Australian Air Chief Marshal Angus Houston said early on Sunday that the agency cannot verify any connection between the signals and Flight 370.
The Boeing 777 disappeared March 8 while en route from Kuala Lumpur, Malaysia, to Beijing with 239 people aboard.
So far, no trace of the jet has been found.
A multinational team is desperately trying to find debris floating in the water or faint sound signals from the data recorders that could lead them to the missing plane and unravel the mystery of its fate.
Finding floating wreckage is key to narrowing the search area, as officials can then use data on currents to backtrack to where the plane hit the water, and where the flight recorders may be.
Beacons in the black boxes emit "pings" so they can be more easily found, but the batteries last for only about a month.
Officials have said the hunt for the wreckage is among the hardest ever undertaken, and will get much harder still if the beacons fall silent before they are found.
"Where we're at right now, four weeks since this plane disappeared, we're much, much closer,'' said aviation expert Geoffrey Thomas, editor-in-chief of AirlineRatings.com.
"But frustratingly, we're still miles away from finding it. We need to find some piece of debris on the water; we need to pick up the ping.''
If it doesn't happen, the only hope for finding the plane may be a full survey of the Indian Ocean floor, an operation that would take years and an enormous international operation.