U.S. officials are taking a closer look at a piece of equipment that could give new insight into one of the worst environmental disasters in the country's history.

Engineers using a massive crane hoisted the so-called "blow-out preventer" out of the Gulf of Mexico late Saturday.

The 15-meter, 300-ton device was supposed to seal off BP's Deepwater Horizon oil well in case of an emergency, but failed, causing the April 20 explosion that killed 11 workers and released millions of barrels into the Gulf.

Federal investigators began taking photographs and video of the device, which is now evidence in the U.S. Justice Department's investigation into the oil spill.

Earlier Saturday, the U.S. official overseeing the response to the oil disaster said the BP well is no longer a threat.

Retired Coast Guard Admiral Thad Allen spoke after BP engineers finished installing a new safety valve on the partially-sealed well.

BP crews are expected to complete drilling a relief well later this week.  The new well will be used to help permanently seal - or kill - the well.

In the meantime, more of the Gulf waters are being opened to fishing.  The National Oceanic and Atmospheric Administration (NOAA) says only about 17 percent of the Gulf remains closed.