Boeing looks for speedy approval after 787 battery tests | Business & Technology | The Seattle Times
Hinderberger reiterated the assertions of top Boeing executives a day earlier that played down the two events that led to the grounding: the battery fire in a 787 parked on the ground in Boston and the smoldering of a battery on a 787 flight in Japan.
He said that the fire in Boston consisted of small flames outside the blue battery box, but that “there was not a fire inside the blue box.”
Boeing's Hinderberger is reported in the Seattle Times to say that the fire in Boston consisted of only "small flames" outside the blue box.
So, apparently there is no need to worry.