Thank God the pilots are alive, irrespective of the events leading to the crash from the pictures the airport fire service did a great job in putting the fire out so quickly. Looking closely at the pictures posted earlier it would seem that the entire port side has smoke / fire damage, yet the starboard side still shows bright white paint.
Its hard to speculate on the cause, but many seem prepared to.
I was involved many years ago in a fire in a Seneca which occured in an engine on finals, I was told afterwards that the time elapsed from me declaring a Mayday to the airport fire services extinquishing the fire was minutes, however I am still haunted by the memories of heat on my back when I ran from the plane upon landing. The heat builds up with incredible speed. Its not surprising the one pilot suffered flash burns.