Vendor approval for plastic bottle producers

Hello all: new to the bottle plastic industry here, we make plastic bottles to pack liquids and pills for pharmaceutical and nutritional products, I'm trying to evaluate my vendors for the first time in this industry and I'm a little lost.

I have multiple questions, in the case of the plastic producers (colors, PET, etc.) do they have to be registered to FDA? some of them are telling me that they are not required but I need to validate that, does a letter of them stating that they abide to FDA requirements would be sufficient? 

Any ideas from the plastic experts would be greatly appreciated.

Thanks in advance

SQFconsultant is correct.  Plastic manufacturers do not need to register with the FDA.  They should, however, be able to provide you with a letter detailing what specific FDA regulations they comply to.  I would ask your vendors for that.