Why would an employer need a pport before hiring you?

I went to an employment agency yesterday to look for work. I've given them my id: my driver's license, social insurance card and they took copies of these. I also had my health card on hand. Then they said they needed my pport as the employer would also need that. They haven't even given me a job yet. They said i can fax a copy of it to them, but i'm considering scanning and emailing it to them instead, because faxing it would require me to bend the pport which i don't want to do. Should i scan it to them? I'm a bit wary because i'm giving them all my personal info. And they haven't even given me job and there is no guarantee they'll give me one. I've gone to a number of agencies and none has asked me for my pport or citizenship info before.