Reuters: Oil giant BP Plc’s (BP.L) shares in New York sank further in early Monday trade after news that the U.S. Department of Justice was taking part in the investigation of the massive oil spill in the Gulf of Mexico. BP shares in New York fell 6.4 percent to $48.84, bringing their drop to more than 18 percent since the close of trade on April 23. London stock markets were closed on Monday for a holiday. U.S. Attorney General Eric Holder’s comments that the Justice Department was …