Crews removed the cap from BP's ruptured Gulf of Mexico oil well late Thursday afternoon, a company spokeswoman said, an important step toward permanently sealing the well.
The operation was the first step in removing the blowout preventer, said BP spokeswoman Jessie Baker. That device failed spectacularly in April, triggering a deadly explosion and oil spill.
Officials planned to replace the blowout preventer with a new one, a major step toward a final fix.
The cap removal was "an important step in the process to remove and preserve the damaged BOP [blowout preventer]," said retired Coast Guard Adm. Thad Allen, the government's point man on the oil disaster. He said work on removing the damaged blowout preventer was expected to commence Thursday night.