An Indonesian official says ping-like sounds were heard in an area where searchers are scouring the Java Sea for the crashed AirAsia plane.

Search operations director Suryadi B. Supriyadi says the signals were picked up intermittently Friday, but it's unclear if they came from the cockpit voice and flight data recorders since no pieces of metal were detected nearby. A day earlier, part of the plane's tail was photographed on the ocean's floor — the first confirmed major wreckage from the plane since Flight 8501 went down Dec. 28.

The black boxes are located in the rear of the plane, but Supriyadi said the sounds were heard about one kilometer (half a mile) from the tail's location.

Transportation safety investigator Nurcahyo Utomo said the signals could not be confirmed.