SOFIA, July 31 (Reuters) - Bulgaria's central bank will ask independent auditors to carry out a thorough review of Corporate Commercial Bank's (Corpbank) books until Oct. 20, it said on Thursday, effectively extending its control over the bank.

The central bank took control over Corpbank on June 20 for three months following bank runs and proposed a rescue plan for Bulgaria's fourth largest lender, which failed to get a parliament approval.

The bank said it now plans ask current shareholders of Corpbank to express interest whether they are willing to provide capital and liquidity support and extend the control over the bank beyond Sept 21.

(Reporting By Tsvetelia Tsolova; Editing by Toby Chopra)