Several weeks ago, I noticed a swollen lithium-ion battery in an older MacBook laptop. Substantial swelling, the battery looks almost twice as thick as normal near one corner. I initially noticed the swelling because it deformed the bottom plate of the laptop. Since then, I have not used the device and currently am storing it in a fire safe location. Unfortunately, the battery is screwed in place inside the laptop and I initially worried that unscrewing might cause further damage or put pressure on the battery. Now, that it has been a while since I noticed the damage to the battery, I assume that it has discharged substantially (though the state of charge was unknown at the time of failure).
Is this assumption safe to make? Can I expect that the danger of fire is lower after safely storing it for this period of time and not observing any changes? Do you think that there is still danger in unscrewing and removing the battery? How cautiously should I need to handle the battery?