A starting point is - was it a brittle fracture or a ductile failure? Usually can tell from visual inspection. Also can you run a sample through a Charpy V notch or other testing?
What alloy was it?
What is past history?
Was a heat treatment involved? (probably not with an ingot)
Any extraordinary loads? My father ran into a case where fins were breaking off a casting as a worker was hitting the casting with a sledgehammer to "remove the sand".