OOC:
I see my last post is a bit messy. Not sure if you understood it. What I want to say is this:
1. There is a door. You may need to spend 1-2 hours excavating it in order to open it as it is opening inside
2. There are 5 more places you could excavate, you have reasons to believe two if them collapsed on a "travelled path"
2.A The 5 places are approximately same sized and it would also take 1-2 hours to fully remove stones, but you may not require to remove all of them to find have a hole to squeeze through
3. You still have option to go back following rails (though you would have to face quite an undead force)