Agence France-Presse: Three weeks into the Gulf of Mexico oil disaster, BP engineers on Thursday worked on a new ‘top hat’ containment dome to put over the ruptured well that has spewed a sea of crude toward the US coast. Oil companies faced growing congressional criticism over safety flaws on the Deepwater Horizon rig which exploded on April 20 killing 11 workers and unleashing the environmental disaster. Frustrated by the failed efforts to stop the massive slick, President Barack Obama sent top …