Published: Sep 19, 2010 8:02 PM EDT
Updated: Sep 19, 2010 5:10 PM EDT

NEW ORLEANS (AP) - BP's blown-out oil well in the Gulf of Mexico has finally been killed once and for all, five months after an explosion sank a drilling rig and led to the worst offshore oil spill in U.S. History.

Retired Coast Guard Adm. Thad Allen, the federal government's point man on the disaster, said Sunday BP's well "is effectively dead."

Crews pumped in cement on Friday to plug BP's well nearly 2.5 miles below the sea floor. The cement had hardened by Saturday, and a pressure test conducted confirmed that the plug would hold.

The gusher was contained in mid-July after a temporary cap was successfully fitted atop the well. Mud and cement were later pushed down through the top of the well, allowing the cap to be removed.

But the well could not be declared dead until a relief well was drilled.