By Annie Barrett
Updated March 18, 2010 at 10:20 AM EDT

Blockbuster Inc. said in a regulatory filing late Tuesday that the company was suffering “significant liquidity constraints” and could have to file for bankruptcy protection due to competition from DVD-by-mail company Netflix inc. and DVD vending machines operated by Coinstar Inc., according to the Associated Press. Shares of Blockbuster dropped 30 percent Wednesday after the announcement. Blockbuster has had to close down 1,300 stores and is looking to close hundreds more.