Engine stall, then blue smoke.

So there I was riding along with a bike in front and another behind me, doing about 50 and then the bike just cuts out! Clutch in and coast to a stop, try to restart it turns over but out comes alot of blue smoke.
So I leave it there and try no more. The rider behind says he saw no symptoms of any kind? So any ideas, worst case scenario? Any ideas of cost? I'm aware you have limited info but forewarned is forearmed. Thanks in advance.

More info required..........no big bangs? Turn over free or laboured?

Suggest pulling plugs as first step.

Hi, no bang big or small, no symptoms of any kind before the engine cut out. And it seemed to turn over fairly easily, but I only thumbed the starter for a few seconds.

Do you use a power commander ?
As mine packed in and wouldnt restart.
But I didnt have blue smoke.
Power commander now off and bike is fine.