I worked at a zoo in a northern country (can't say which as it'll give it away) which had a white tiger, and was quite famous for it. One day the zoo announced the tiger had died of 'natural causes'. Whilst working there a few years after he died, I was told by a keeper that there was actually a problem with the electric fencing in his enclosure that the zoo managers refused to pay to get fixed, thinking it would be fine.
He was electrocuted to death a few weeks after they found the problem.
They covered the whole thing up by saying they weren't sure how he died, but that he was old. It's still a zoo secret to this day.