Does anyone know what level the SBA underwrites the bank/lender submission for the PPP?

Merchant of mine said that his bank approved all the docs he sent in and confirmed they submitted to SBA, he asked me do I know if the SBA does additional UW on the submission or do they rely on the bank/lender to do that and basically just auto approve it once it hits their system or do they re underwrite the file before approval/decline?