Complex sentence: Some were conscious and lucid, talking to rescuers, but died of crush syndrome soon after the weight was removed from their bodies due to the sudden release of muscle myoglobins having built up in the limb, causing renal failure.
Split into simpler sentences: Some were conscious and lucid, talking to rescuers, but died of crush syndrome soon after the weight was removed from their bodies. This was due to the sudden release of muscle myoglobins having built up in the limb, causing renal failure.