Shadowleaf, with the help from Kinden does find that it's a door.
The others keep their eyes on the curve of the passage ahead, which curves out of sight to the north some 30' in front of the group.
With a little more pressure and searching, Shadowleaf finally finds what he did not know he was looking for, and the door cracks open enough for him to get his fingers in and open the rest of the way. Looking again, with the help of the light form the spell, he notes that what he had found was a pressure stone that when pushed, forced the door out to where you can open it manually. After opening the door after listening for any thing beyond, he notes that there is another passage heading south. This one cleaner, but narrower. One human sized person would not have to duck from the low ceiling, but neither would he be able to swing a weapon down on anyone. THe width, however was wide enough for a sword wielder to swing back and forth, as long as no one else was at his side.
The tunnel floor is about two feet higher then the sludge level in the passage the party originated from, so relatively dry. There are smuges and tracks from the sludge going down the hall, though it's anyone's guess whether its from people coming or going, or whether it was created by people at all.
On closer inspection to the inside of the corridor, Kinden and then Shadowleaf notice that there are torch sconses with unlit torches in them... un used and fresh torches.