What are the spots inside my celery?

What are the spots inside my celery?

I don't have a photo ... but ...

All the celery is crisp, freshly bought from the store.

1/2 the celery bunch is completely fine.

1/2 of the bunch have these slightly discolored and slightly indented long spots inside the celery stalk that go for about 1/2 the INSIDE of the stalk. The outside is fine, and the rest of the celery stalk is fine.

Is this a Celery infection?

Celery bacteria or virus?

Is this an insect? (I don't see signs of eggs or webs.)

And most importantly ... IS IT STILL EDIBLE?