Indonesia's search and recovery agency says a sonar image appears to have found the wreckage of AirAsia Flight 8501 upside down on the floor of the Java Sea, CBS News has confirmed. It is unclear whether or not the plane has been found intact. The development comes on the fourth day of the effort to find the remnants of the downed airliner that crashed early Sunday. The cause of the crash is still unknown and searchers are still attempting to recover the plane's black box to get an explanation of how the crash happened.