Immigration officers in Toronto Airport are quite nice(relatively). What happened to me was that I crossed the CA-US borders last time by greyhound. That officer asked me American IDs. I showed him mine. Then he kept asking me if I tried to work or stay illegally in US. Fortunately my status is good. After 30 minutes, he let me go. Next female officer was much nicer. She started checking my bag. The first thing she asked to show was my documents. When she found my status is all right, she walked to that officer. Very quickly, she returned, and said, "You are all set.".