NEW ORLEANS — The Gulf Coast found itself in an odd moment of limbo Saturday: The oil has been stopped, but no one knows if it's corked for good.
The clock expired on BP's 48-hour observation period and the government added another day of critical monitoring. Scientists and engineers were optimistic that the well showed no obvious signs of leaks, but were still struggling to understand puzzling pressure readings emerging from the bottom of the sea.
It's possible the past three days will be only a brief reprieve from the flow of oil bleeding into the gulf. Retired Coast Guard Adm. Thad Allen, the government's point man on the crisis, decided Saturday that after the testing was complete, the cap will be hooked up through pipes to ships on the surface that will collect the oil.
That likely means releasing crude back into the water temporarily to relieve pressure. It still would not be gushing at the rate it had been before BP's latest fix.
And even though it was only days since the oil was turned off, the naked eye could spot improvements on the water. The crude appeared to be dissipating quickly on the surface of the gulf around the Deepwater Horizon site.
Members of a Coast Guard crew that flew over the wellhead Saturday said far less oil was visible than a day earlier. Only a colorful sheen and a few long streams of rust-colored, weathered oil were apparent in an area that was covered by huge patches of black crude weeks earlier. Somewhere between 94 million and 184 million gallons have spilled into the gulf, according to government estimates.
BP began Saturday saying it was feeling "more comfortable," though Kent Wells, a BP vice president, cautioned the evaluation was not over. BP and the government want to make sure the well can stay bottled in case of a hurricane, when ships would have to leave the area.
Wells said engineers glued to an array of pressure, temperature, sonar and other sensors were seeing no evidence of oil escaping into the water or the seafloor. Undersea robots were also patrolling the well site for signs of trouble.
BP shut valves in the cap Thursday, stopping the flow of oil into the gulf for the first time since the April 20 explosion on the leased oil rig Deepwater Horizon killed 11 workers and unleashed the spill 5,000 feet below the sea.
Concern that the cap could cause oil to break out of the well at the seafloor have lessened.
Pressure readings Saturday morning were 6,745 pounds per square inch and rising slowly, Wells said. The figure was below the 7,500 psi that would have reassured scientists the well was not leaking, but still high enough that it could be all right.
A low pressure reading, or a falling one, could mean the oil is escaping. Wells said pressure continued to rise very slowly.
The most likely reason the pressure is low is more oil has bled out than estimated, experts say.
Either way, the cap is a temporary measure until a relief well can be completed and mud and cement can be pumped into the broken well deep underground to seal it more securely than the cap. That means the best fix still won't be completed until later this summer.