담기다 means to be put, so it's already a passive voice. But what means 담겨지다 and 담겨져있다? Where they can be used?
담기다, 담겨지다 => This means "has been put in" and implicitly, additionally "it just happened." For example, "사과가 봉지에 담기다." means "The apple has been put in the plastic bag." (Someone has put the apple in the bag.) and it just happened.
담겨져있다 => This means the status meaning "be (already) (put) in". For example, "사과가 봉지에 담겨져있다." means "The apple is in the plastic bag." (Someone put the apple in the bag in the past, so the apple is in the bag now. When you see the apple contained in the bag, you say "사과가 봉지에 담겨져있다."
This -아/어 지다 ending after a passive verb is both interesting and controversial. It could be considered double passive, but perhaps not conclusively so, since -아/어 지다 can also mean a state change.
For example, 어둡다 (is dark) is just an adjective (sometimes called "descriptive verb"), so that 어두워지다 can't be a passive but just a state change from bright to dark. There are many such adjective-based -아/어 지다 forms: 좋아지다, 나빠지다, 커지다, 뜨거워지다, etc.
There indeed are usages that look like double passives, though, like 잊혀지다 (be forgotten) for example, which is -아/어 지다 attached to 잊히다 (be forgotten) which is already in the passive form. But even for these, if you think of the -아/어 지다 as a state change, then it might not necessarily be a problem. We might just think of it as passive with a state change, or just a passive form with an emphasis.
Whether it is a problem or not, it is probably a good idea not to overuse such phrases. Recently, though, there is a very annoying example (at least to me) of it in wide use, which is 보여지다 ("It appears"). It seems everyone on TV and radio says 보여집니다 when 보입니다 is already clear and natural. It's okay to hear it once in a while, but they always stick to this longer word which may also be redundant for some reason. I can never understand why they do it.