Wondering what caused the apocalypic outbreak of walkers on "The Walking Dead"? Keep wondering. Because the show's writers say they don't know either -- and aren't terribly worried about it.

"Internally, we don't know where the zombie outbreak started, how to cure it, anything like that," show runner Glen Mazzara told TheWrap. "We haven't really discussed it. We're more interested in the continuing storylines."

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The comic series that inspired the show doesn't address what caused the outbreak of zombiedom. The show's writers -- including comic book creator Robert Kirkman -- say they won't address it either, even though they feel free to split from comic book storylines.

"That's something that's not really addressed in the book. And that's something that we'd like to keep," Mazzara said. "This show is about our characters. And about them trying to stay alive, hold on to their humanity, find a safe place, hopefully rebuild civilization. Just everything's collapsed. So they're under incredible duress. It doesn't feel right that they would have those answers, and even if they did have those answers, what would they do with them?"

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He added: "I think part of the success of the show is that it feels immediate. It feels like we're following the little guys. And they don't have the answers and they desperately need them to survive."

The show's writers spoke Saturday at the Television Critics Association winter press tour, where AMC also announced that the series -- its biggest hit -- will get 16 episodes in its third season. The current, 13-episode second season continues Feb. 12 after a midseason break.