If you aren't sure if the modeling agency is a scam then you should do a few things:
1. GOOGLE. Google the agency name + scam. It will tell you right off the bat if it is a scam.
2. Go to meet with them, BUT run out of there if they ask for money, force you to take photos or anything that involves money. It is a pure scam.
If an agency is a scam the internet will tell you, but if you are not sure you can always go and check it out and leave if it seems weird.