Canada visa Biometric in US - Passport kept or returned?

[im42]

If I go to do my Biometric for a Canada Visitor visa process at a United States center, will the CIC keep my passport for further processing or is the passport supposed to sent separately at a later date? I actually need my passport for some other process elsewhere right after this Biometric and was wondering if I can submit the passport later on to CIC (and not during the Biometric).