(CNN) -- As the cement hardens Friday in the crippled oil well in the Gulf of Mexico, federal officials are sounding increasingly optimistic that the end is in sight in the drive to permanently seal the well.
BP finished pouring cement down the well on Thursday in an operation known as a "static kill," completing the job earlier than expected. The process took six hours.
The cement was poured on top of 2,300 barrels of heavy drilling mud sent down from a ship on the surface Tuesday, pushing oil back into the well reservoir.
Before word came that the cementing had been completed, retired Coast Guard Adm. Thad Allen said the development would amount to a "significant milestone" in the long-running fight against the BP oil spill. Allen is the federal point man in the oil spill effort.
He said the cementing phase of the "static kill" operation is not the end of the process, "but it will virtually assure us there's no chance of oil leaking into the environment".
"We will have created a significant milestone and made a major step forward probably by tomorrow [Friday] when the cementing is done," Allen told reporters. Although Allen expected the job to take until Friday, BP announced late Thursday that the work had been finished. CNN
