The two things I've learnt is that (correct me if I am wrong):

1. We are not allowed to buy shares in companies that deal with haram things like alcohol, drugs and pornography etc.
2. Companies that deal with interest.

I was looking at buying shares in shariah compliant companies and saw Amana Growth and Amana Income. Apparently, in their portfolio they have companies like Nike and Apple. How does Amana know if these companies deal with interest or not?

I would have thought that most of these big western companies borrows lots of money from the bank?