( CNN ) -- A blowout preventer that may hold important forensic evidence as to why it failed , triggering the world 's largest accidental oil spill , has been brought to the surface of the Gulf and placed on a vessel , officials said Saturday night . The device `` was taken into custody by the U.S. Department of Justice as evidence in its ongoing investigation into the incident , '' BP said . The blowout preventer was lifted to the surface at 8:53 p.m. ( 9:53 p.m . ET ) . Adm. Thad Allen , the government 's national incident commander , said the huge blowout preventer `` is considered evidentiary material . '' The April 20 explosion killed 11 workers aboard the Deepwater Horizon rig . A new blowout preventer was installed atop BP 's plugged well late Friday . Crews had to flush out potential hydrates -- crystals that form in cold temperatures -- before the old blowout preventer was hauled about the Q4000 surface vessel . Joint investigation teams , engineers and the Department of Justice will pore over the recovered device . `` I 'm very pleased to announce that with the new blowout preventer on [ and ] the cement that was previously put in ... this well does not constitute a threat to the Gulf of Mexico , '' Allen said earlier Saturday . He provided details on the installation of the new blowout preventer late Friday . `` This is an important milestone as we move toward completing the relief well and permanently killing the Macondo 252 well , '' he said . Once the new device is successfully tested , BP will drill the last remaining feet of a relief well to intercept the damaged well . Finally , the company will execute a `` bottom kill '' -- a measure that fills the well from the bottom with mud and cement . That is believed to be the only way to seal the well for good . `` Depending upon weather conditions , mid-September is the current estimate of the most likely date by which the relief well will intercept the MC252 well , '' BP said in a statement Friday , using the shorthand reference to the well 's official designation , Mississippi Canyon Block 252 .
2010 : The failed blowout preventer is brought to the surface . A new leak preventer has been placed on the capped well . BP will continue drilling on its Gulf Stream well .