As the Coast Guard searched for 11 crew members missing after a drilling rig exploded and sank in the Gulf of Mexico, authorities turned their focus to controlling an oil spill that could threaten the fragile ecosystem of the Louisiana and Mississippi coasts. The Deepwater Horizon had burned violently for nearly two days until it sank Thursday morning. The fire's out, but as much as 336,000 gallons (1.27 million liters) of crude oil a day could be rising from the sea floor 5,000 feet (1,524 meters) below, officials said. 'If it gets landward, it could be a disaster in the making,' said Cynthia Sarthou, executive director for the environmental group Gulf Restoration Network. BP PLC, which leased the rig and took the lead in the cleanup, said Friday it has 'activated an extensive oil spill response,' including using remotely operated vehicles to assess the subsea well and 32 vessels to mop up the spill. BP Chief Executive Tony Hayward said the company will do 'everything in our power to contain this oil spill and resolve the situation as rapidly, safely and effectively as possible.' He says the company can call on more resources if needed. Ed Overton, a Louisiana State University environmental sciences professor, said he expects some of the light crude oil to evaporate while much of it turns into a pasty mess called a 'chocolate mousse' that ultimately breaks apart into 'tar balls,' small chunks of oily residue that can wash ashore. 'It's going to be a god-awful mess for a while,' he said. 'I'm not crying doomsday or saying the sky is falling, but that is the potential.' The Coast Guard early Friday was searching for the missing, but some family members said they had been told that officials assumed all were dead. Most of the crew -- 111 members -- were ashore, including 17 taken to hospitals. Four were in critical condition. The accident shows that drilling is not safe, said Abe Powell, who heads Get Oil Out!, created after a 1969 platform accident off Santa Barbara, California, fouled miles of ocean and beaches with wildlife-killing goo and spawned the environmental movement. 'When oil companies say drilling is safe now and we won't allow any accidents ... we know that's not true,' he said. Weather forecasts indicate the spill was likely to stay well away from shore at least through the weekend, but if winds change it could come ashore more rapidly, said Doug Helton of the National Oceanographic and Atmospheric Administration's office of response and restoration. The Coast Guard, which was leading the investigation, hadn't given up the search early Friday for those missing from the rig, which went up in flames Tuesday night about 41 miles (66 kilometers) from the mouth of the Mississippi River. Four who made it off safely were still on a boat operating one of several underwater robots being used to assess whether the flow of oil could be shut off at a control valve on the sea floor, said Guy Cantwell, spokesman for rig owner Transocean Ltd. The Marine Spill Response Corp., an energy industry cleanup consortium, brought seven skimmer boats to suck oily water from the surface, four planes that can scatter chemicals to disperse oil, and 94.6 miles (152 kilometers) of containment boom, a floating barrier with a skirt that drapes down under the water and corrals the oil. Another 500,000 feet (152,400 meters) of boom were on the way, BP spokesman Tom Mueller. 'Right now we are over-responding with resources to manage the potential spill here,' he said. 'We will be well-prepared to manage whatever comes.' He said about 1.1 mile (1.8 kilometer) of boom was in the water by Thursday evening. Family members of two missing workers filed separate lawsuits Thursday accusing Transocean and BP of negligence. Both companies declined to comment about legal action against them after the first suit was filed. The U.S. Minerals Management Service, which regulates oil rigs, conducted three routine inspections of the Deepwater Horizon this year -- in February, March and on April 1 -- and found no violations, MMS spokeswoman Eileen Angelico said. ------ Associated Press Writer Noaki Schwartz reported from Los Angeles, Holbrook Mohr from Jackson, Mississippi, Mike Kunzelman, Cain Burdeau and Alan Sayre in Louisiana, Chris Kahn in New York and Sofia Mannos of AP Television News contributed to this report. 