I do not think there is any *direct* threat--only airborne pathogens could escape on their own and that would require a lot more than just thawing out. However

I do not think there is any *direct* threat--only airborne pathogens could escape on their own and that would require a lot more than just thawing out. However, I do think there's some risk--looting. Something dangerous might be unknowingly carried out of there and there's a variety of pretty nasty things they might have samples of.