Published: Aug 13, 2010 7:21 PM EDT
Updated: Aug 13, 2010 4:21 PM EDT

NEW ORLEANS (AP) - BP's broken Gulf of Mexico oil well is not yet plugged for good, and work on what's been touted as the permanent solution will need to continue, the federal government said Friday.

Retired Coast Guard Adm. Thad Allen, the government's point man for the spill response, said officials were still evaluating the best way to finish the relief well that is part of the "bottom kill" operation. But he said that crews must move forward drilling the relief well.

"The relief well will be finished," he said. "We will kill

the well."

BP had thought the mud and cement pumped in from above the leak may have essentially killled the well. But the relief well will allow engineers to pump in mud and cement from below in an attempt to permanently seal the well.

Work on the wells was stopped this week because of bad weather.

The decision to resume work on the relief wells means a key milestone in the crisis that crippled the Gulf Coast's economy and ecosystem remains days off. However, Allen has repeatedly insisted on an "overabundance of caution" when it comes to permanently plugging the well.

Officials had been testing the pressure beneath the cement plug currently in place. Steady pressure would indicate the presence of cement in the space between the inner piping and the outer casing, likely indicating a permanent seal.

But because pressure rose during the testing, the scientists concluded that space still needs to be plugged in.

It also would have been difficult to say the "bottom kill" was unnecessary after promising it for weeks as the ultimate solution, said Eric Smith, associate director of the Tulane Energy Institute.

"That's been the mantra all along, that they wanted to do the bottom kill," he said.

The flow of oil into the Gulf has been halted since July 15, when a temporary cap over the well was able to contain the spill.

But officials have stressed for weeks that only a bottom kill will ensure the well is no longer a danger.

Before July 15, the oil leaked almost unimpeded for nearly three months. The crisis began on April 20, after an explosion on the BP PLC-leased Deepwater Horizon drilling rig that killed 11 workers.

Officials don't yet know the cause of the explosion, or why machinery designed to prevent the unchecked flow of oil failed to work.