pbr BP has hit a snag in its latest effort to curb the Gulf of Mexico oil spill.br ppbr The company's latest plan is to siphon off some of the oil but first robot submarines must cut away what is left of the ruined offshore well's leaking riser pipe. Then a containment cap can be lowered over the remaining wellhead assembly, enabling BP to funnel crude to the surface.br ppbr But the diamond-tipped saw being used to cut through the pipe became stuck, and BP is employing robots on the seabed to free it, a difficult task one mile deep.br ppbr Tar balls and other oil debris from the giant, fragmented slick reached Alabama's Dauphin Island, parts of Mississippi and were less than ten miles from Florida's northwest Panhandle coast. The region's vital seafood and tourism industries are at risk from America's biggest oil spill ever.br ppbr President Barack Obama, facing one of the biggest challenges to his presidency, is under relentless pressure to stop the leak.br ppbr BP is now facing a criminal investigation and has lost one-third of its market value or about $67 billion (£46 billion) since the April 20 rig explosion that killed 11 and triggered the mile-deep gusher.