It's the usual TV bovine ordure. There was a coal fire in a bunker in boiler room 6. This was a common thing and they fixed it in the usual way, by removing the coal and putting it into the furnaces. It was all over by about lunch time on the Saturday.
The heat distorted the adjacent bulkhead a little and there is debate about whether this later did any harm. If it did, it was minor compared with the rest of Titanic's problems.
The TV rubbish stemmed from someone getting excited about the bulge on the starboard side of the wreck that was caused by the impact with the bottom.
I agree with Dave! I've heard this story before... When the Americans were exploring the wreck, they found an massive 30 foot wide hole, ripped in the starboard side hull. Now, with typical revisionist fervor, people came out of the woodwork claiming that this hole could only of been caused by a massive explosion in the coal bunker of boiler room 6. Which, of course, was the REAL reason the Titanic sunk. Mmmmmmm, yes. That really happened, didn't it!
These people ignore a few basic facts, like the fire being out at the time of the collision. The hole being forward of the bunker and above the waterline. Not to mention that nobody witnessed an explosion catastrophic enough to produce such a hole in the first place... As Dave said, it's generally accepted that this hole was caused by the impact with the bottom...
Enough said on this theory. The hole in the starboard side is located at one of the doors and the educated guess is that when the water filled bow struck the bottom and forced the hull to bend and contract that the water inside needed an exit route and exploded out the hole visible now where this door was.