Solved Uprooted Blocks

I logged on my server this morning, and one of the players asked me for help about this deep trench he found in the middle of his town. It's width is just one, but it's length seems to go on for quite a while. This also wasn't a a casual world edit mistake that happen every so often, the blocks where uprooted as well. We found bedrock and redstone ore across the surface, and grass at the bottom. My question is, is there any plugin known to cause this? If so, what plugin would it be and how would we stop this? Also, when we try to fill it in, it happens again in the same spot.

Plugins:
Multi-Inv, World Edit, ZNounce, BukkitCompat, ZPort, Vault, LogBlockQuestioner, DeathNotifier, Multiverse - Core, ZPluginManager, PermissionEX, LogBlock, Questioner, CapsGuard, WorldGuard, IConomy, Register, PEXRank, Essentials, Jobs, Towny, Multiverse - Portals, Permissions, ZPVP, BKCommonLIB, modifyworld, ZSpawn, HeroChat, Multiverse - NetherPortals, LWC, ChestShop, MobArena, TownyChat.

 

That sounds like a chunk error. Happends every once in a while.

 

someone may have hacked you? - all i can say. If not, Astro's right.

 

Wow, that would be the last thing I would of thought of. Thanks lol.

Thank you for your response

EDIT by Moderator: merged posts, please use the edit button instead of double posting.