Once the visa office begins processing your file they will commence with document background checks.
At this stage your ECAS status should now read “In Process” with the extra line in the detail “Your application was reviewed and we started processing on <Date>”.
This document background check will include ascertaining the authenticity of your documents, and since they use some third party companies for this it could take a varying level of time depending on your visa office, the complexity of your case, and even the speed of the individual visa officer looking at your case. They may also perform employment verification checks which will involve telephoning both you (whilst at work) and your employer to ensure you give the same answers on their questions about your employment. Only a small percentage of applicants are likely to receive employment verification. Only if they are unconvinced by any of the work experience documents you sent, or if your application is one of the random spotchecks they do to prevent fraud, will they actually perform the verification.
Visa office may request further documentation from you during the processing phase, which can come by email. They may also ask for a few things (PCCs or fresh forms) at the same time as medicals.
Once the document background checks are completed satisfactorily, the visa office will write to you requesting you to complete medicals and also requests RPRF (Right of Permanent Residents fee). They may also ask for updated documents such as PCCs and fresh forms at this stage. Please note that New Delhi visa office will also request passports at this stage. Most other visa offices will not request passports until they are about to finalise the application.