Investigators of the missing Malaysian Airlines flight MH370 may be wrong in identifying the pings that were thought coming from the plane under Indian Ocean.

Authorities admitted to suspect the origin of two out of four pings that were earlier detected from the missing Boeing 777. According to a Daily Mail report, a senior Australian naval officer has expressed his doubts about the pings.

He said he "increasingly suspects" some of the signals that were picked up by the detectors during the search. During the underwater search, U.S. Navy's Bluefin 21 detected four pings thought to have originated from the missing plane's blackbox.

James Lybrand, Australian naval commander, said two of those four pings were "too weak to have been from a man-made device." The missing Malaysian aircraft went missing on March 8 and two months after continuous global search efforts, the mystery continues to deepen.

The report noted during underwater search in April, investigators picked up two pings on April 5 measuring a frequency of 33.3 kHz. The vehicle detected two more pings three days later on April 8 at the frequency of 27 kHz.

Pings from these two days were much lower than what the black box was originally designed to emit. Normally, the frequency should measure 37.5 kHz. Signals from April 5 were still considered potential leads from missing plane. This was considered a possibility due to the "weakening batteries or vagaries of deep-sea conditions."

But there was "pretty large jump" between the frequencies measured on the two previous dates, the officer cited.

The report said the officer revealed that authorities still consider April 5 signals "consistent with black-box locator beacons." One out of two signals on this day was held for as long as 2 hours and 20 minutes.

Wall Street Journal noted Joint Agency Coordination Centre, the Australian agency leading the search mission, did not "immediately respond" when asked to comment on Lybrand's analysis.

On May 14, Press TV reported Chief Coordinator of the JACC Angus Houston said the four underwater pings were "still the most promising leads."

"Analysis on all four detections is continuing... At this point in time, it is too early to discount any of the acoustic detections," told Angus Houstan. He is the retired officer of the Royal Australian Air Force and now leads the MH370 search mission.

Quite often, the tragedy of missing Malaysian Airlines flight MH370 has been compared to that of Air France 447. But he explained there is "big difference" to the two incidents mainly due to the absence of "last known position" of MH370, which was not the case for Air France flight.

Air France reportedly had a "very good last known position" and the plane was found close to this position. The missing Malaysian aircraft disappeared with 239 people on board but no traces have been located so far.