BP has finally succeeded in halting the seepage of oil from the damaged oil well in the Gulf of Mexico. By closing off valves in a cap bolted to the top of the Macondo last week, BP Plc stopped the stream of oil for the first time in almost three months.

BP is reportedly evaluating data via a pressure test to determine whether its leak of oil into Gulf of Mexico oil well remains sealed. The test is said to measure the pressure inside the well, and may continue for about two days, according to a BP e-mail statement.

While there is a sigh of relief that the oil is no longer flowing into the Gulf, it is still unclear if the well is permanently sealed. Government officials are also monitoring the cap on BP's blown-out well.

BP chief operating officer Doug Suttles confirmed that the cap is the best way to ensure no more oil leaks into Gulf waters until engineers can seal the well with cement in the coming weeks.

"We are hopeful that, if the encouraging signs continue, we will be able to continue the integrity test all the way until we get the well killed.... Right now there is no target to open the well back up to flow." Suttles said.

Philip Adams, an analyst at Gimme Credit LLC in Chicago commented: “I would prefer that the pressure test goes well, that it holds pressure. And that they are in fact, able to say that there has not been damage to the wellbore below the seafloor.”

Nonetheless, BP engineers say they are prepared to reopen the well if the pressure test shows signs of damage to the well. In that case, crews would use the current cap system to siphon oil into surface vessels.

The disaster, tagged as the biggest oil spill in U.S. history, followed an April 20 explosion aboard the Deepwater Horizon drilling rig.

The well has been spewing 35,000 to 60,000 barrels of oil a day, according to a U.S. government-led panel of scientists.

“It felt very good not to see any oil going into the Gulf of Mexico ….. “We’re very encouraged.” BP Senior Vice President Kent Wells told the media on a conference call.

Suttles also said that drilling crews have only 30 meters remaining to finish a relief well that will be used to fill the original well with cement, adding that the final operation to kill the well may be completed by late July or mid-August.

Meanwhile, BP’s confirmation that it had stopped the flow from the well pushed BP’s shares up 7.6 percent to $38.92, the highest value in over a month.

Success in stopping the leak, even temporarily, “has the market excited that this could lead to an earlier-than-expected containment of the well, from expectations of mid-August to within the next several days,” Brian Gibbons, an analyst at CreditSights Inc. in New York, said in an interview.