Chosen Solution
While trying to remove the battery I punctured one of the cells but it still isn’t out yet. There was a tiny puff of smoke at first for a second but nothing now. I am still trying to get all the cells out. Should I be worried about it going up in flames at any moment?
Now that it has been a day, I would put a large piece of electrical tape over the hole. Then very carefully attempt to remove it and I would do it outside and stop at the moment anything suspicious starts. Wear rubber gloves and eye protection.