Hmmm. Auditing!
Most of the times, auditing relates to financial matters. But, there are also other types, IT auditing, FDA audits for clinical procedures, etc. etc.
The INS audit could be for finances, their IT systems, Visa, GC granting processes, etc (to check all steps/verifications were done). Barring finance matters (in which all books need to be poured over), for others the audit would be pretty random (ie. random checks with audit escalation on any failure). For the audit process to be successful, the auditors would need the complete help of the employees with details, documents, processes, etc.
I do not think this audit would be an inventory check but more of INS finances and the INS regulatory system. I also do not believe an audit can shut down VSC. Then what would happen to businesses, hospitals, etc in a similar scenario. No where have I come across where the company has to completely shut down for auditing.
FYI, Even a SEC investigation and re-audits do not need the likes of Worldcom, Enron, Global Crossing, etc. to shut down operations. They still keep their offices open and do business.
There might be a slow down in work because the auditors need to get hold of a few people to get information but then they always don't keep this people around all the time during the audit. Hence, whole departments are not closed but only relevant information obtained from the relevant personnel.
Additionally, even if INS closes down for any reasons NONE OF US CAN DO ANYTHING ABOUT IT.