Photo timeline of Gulf oil spill (54 images)

The mobile offshore drilling unit lowered a pollution containment chamber to the bottom of the Gulf of Mexico off the coast of Louisiana to hopefully contain a oil leak some 5,000 feet below the surface. The structure -- as tall as a four-story building and weighing 100 tons -- was to be placed over the wellhead. The measure is a stopgap meant to hold spewing oil, which workers hope can then be siphoned to surface tankers, until the source can be capped. Unfortunately, engineers didn't anticipated gas hydrates -- crystal formations of natural gas and water formed under pressure -- would clog the structure's opening, but crystals did form, clogging the opening at the top of the containment box that was to have channeled the oil into lines connected to a barge. (UPI/Patrick Kelley/U.S. Coast Guard)

U.S. officials close areas affected by the spill to fishing for an initial period of 10 days. (UPI/A.J. Sisco)

U.S. President Barack Obama addresses the media at Coast Guard Station in Venice, Louisiana on May 2, 2010. President Obama conducted a personal assessment of the aftermath of the explosion of the BP oil rig. BP starts to drill a relief well alongside the failed well, a process that could take two to three months to complete. UPI/Patrick Kelley/U.S. Coast Guard

BP CEO Tony Hayward states that BP will take full responsibility for the oil rig explosion aftermath and pay all legitimate claims and the cost of cleanup. UPI/A.J. Sisco