Kenner , Louisiana ( CNN ) -- A `` black rain '' of drilling fluid and a roar of escaping gas erupted from the doomed Deepwater Horizon shortly before the explosion that sank the oil rig , the captain of a nearby ship testified Tuesday . Alwin Landry 's supply vessel Damon Bankston was alongside Deepwater Horizon at the time of the blast . Landry said the first sign of trouble was when drilling `` mud '' -- a mixture used to pressurize and lubricate the drills -- began falling onto the stern of his ship . `` We essentially closed the wheelhouse doors . I went to the port side , and I looked out up at the derrick . That 's when I see the mud coming out of the top of the derrick , '' Landry told investigators Tuesday . When he radioed the rig 's bridge , Landry said , its captain told him there were problems with the well and he should move his ship away . Seconds later , he said , he heard `` the percussion and the slight flash of green '' of an explosion . Deepwater Horizon sank April 22 , two days after the explosion . The blast left 11 people aboard the rig presumed dead and uncorked a gusher of oil that has been spewing an estimated 210,000 gallons ( 5,000 barrels ) of crude oil a day into the Gulf of Mexico . Landry 's testimony came on the first of two days of hearings by a joint Coast Guard-Interior Department panel . His ship picked up the rig 's survivors , and Landry said the rig 's captain , Curt Kutcha , told him he had tried to activate a `` kill switch '' that would cut off the well before abandoning the structure . The crew did not know whether it was working when they fled the burning rig , Landry told investigators . The federal Minerals Management Service , the Interior Department agency that oversees offshore oil exploration , inspects drill rigs once a month , MMS inspector Eric Neal told the panel . Test results from the rig 's blowout preventer , a massive device meant to cut off the well in an emergency , and drilling mud weights are reviewed as part of that process , he said . Neal inspected the rig April 1 and found no violations , he testified . But he did not inspect the preventer 's emergency disconnect system , he said . The companies involved in the drilling process are blaming each other for the disaster . The chairman of well owner BP 's American subsidiary , Lamar McKay , told a U.S. Senate committee Tuesday that rig owner/operator Transocean was responsible for the rig 's operation and for testing its blowout preventer . But Transocean CEO Steven Newman told the Senate Energy and Natural Resources Committee that the well 's cementing , or the casing that holds the well in place , must have failed . BP , as the well 's owner , was responsible for designing the casing , while oilfield services contractor Halliburton performed the cementing . `` Without a failure of one of those elements , the explosion could not have occurred , '' Newman said . And Halliburton 's chief safety and environmental officer , Tim Probert , told the committee that responsibility lay with either Transocean or BP . During the cementing of the well , Halliburton simply followed BP 's instructions , he said , and the blowout preventer was Transocean 's responsibility .
Deepwater Horizon supply vessel was alongside Deepwater Horizon at time of blast . Landry said first sign of trouble was when drilling `` mud '' began falling onto his ship . Captain radioed rig 's bridge and was warned he should move his ship away . Rig sank two days , two days after explosion ; one presumed dead ; oil still gushing into the Gulf of Mexico .