OIL WELL SEALED (FOR NOW)…. As of an hour ago, the wellhead gushing oil since the Deepwater Horizon explosion was fully contained.

BP said Thursday that it has stopped oil from leaking out of its blown-out well in the Gulf of Mexico. The gusher has been throttled for the first time since the April 20 blowout on the drilling rig Deepwater Horizon.

Kent Wells, BP’s senior vice president of exploration and production, told reporters that a new capping mechanism shut off the flow of crude from the Macondo well at 3:25 p.m. EDT. He made the announcement after engineers gradually shut off valves to test the pressure. The engineers are monitoring the pressure to see whether the new cap and the well bore hold.

Watching the live feed, it’s clear the oil that was gushing into the Gulf of Mexico has, at least for now, stopped entirely. To put it mildly, it’s a welcome sight.

The new containment mechanism has been delayed a bit in recent days, but officials shut the various valves today as part of a long-awaited “integrity test,” and so far, so good. The “pressure test” will continue over the next 48 hours.

So, are we in the clear? Crisis over? Not yet. The seismic tests will tell us whether to the cap should stay on.

If the well can handle the high pressures, BP could leave the well shut in, and it would not further pollute the gulf.

White House press secretary Robert Gibbs discussed the hazards of the test Wednesday. “If the structural integrity of the well bore isn’t strong, what you’ll get is oil . . . coming out into the strata,” he said. That could mean leaks “from multiple points on the seafloor.”

If the pressure readings are too low, BP will abandon the test. The well will be reopened and gush anew.

If the new mechanism either has to be removed or fails, MSNBC notes that BP still “expects to be able to siphon up most if not all of the oil starting next week.”

Also note, even under the best of circumstances, if the current containment mechanism continues to operate as it is right now, it’s still not a permanent solution. That’s likely to come from the relief wells, which are very close, but have been halted during the pressure test.

For the first time in a long while, there’s reason for optimism — cautious optimism.

Our ideas can save democracy... But we need your help! Donate Now!

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.