BP's shares rallied earlier this week on speculation that the company was seeking investment partners from the Middle East to help fend off potential takeover bids. BP has said it would welcome new investors but does not plan to issue new stock to help pay for the clean-up. The company's shares have lost around 50% of their value since the April 20 explosion on the Deepwater Horizon oil rig, which killed 11 workers and left a ruptured BP well spewing crude oil into the Gulf. Also Wednesday, BP confirmed that it had received a letter from the U.S. Justice Department demanding advance notice of any asset sales or significant cash transfers. Normally, the Justice Department does not require notice of such deals. "We have received the letter, and have not yet responded," BP spokeswoman Sheila Williams told the AP. "We will be responding in due course."