BP PLC's (BP, BP.LN) plans to test the integrity of an overflowing well in the Gulf of Mexico have been delayed again because of an "unexpected," problem with a piece of equipment, a company senior vice president said Thursday.

The postponement is just another setback for a company under pressure to contain the well, which has caused one of the worst environmental disasters in the history of the U.S. The Macondo well began gushing shortly after the April 20 explosion and subsequent sinking of Transocean Ltd.'s (TNT.YY) Deepwater Horizon drilling rig.

On Wednesday night, the U.K. oil major had to postpone the test after a leak was found in a choke line, a piece of tubing that was attached to the cap, which was placed on the well in the last week, Senior Vice President Kent Wells said during a morning teleconference.

The new cap is designed to either entirely shut in the well or at least increase the amount of oil that can be captured from the well.

However, before BP can decide whether or not it can use the cap to seal the well it must perform an integrity test. The company still plans to go forward with the test and will issue a news releases as soon as it does so, Wells said. While this test could start later on Thursday, unexpected issues with other equipment could always further delay the procedure, he said.

The company had originally planned to begin the procedure on Tuesday but the U.S. government ordered a 24 hour delay to address concerns that test could lead to an another uncontrolled leak.

"This last-minute evaluation was due to an overabundance of caution," retired Coast Guard Admiral Thad Allen, the federal response commander said Wednesday evening.

Once the test starts, engineers and scientists will closely watch the pressure levels inside the cap. If in the first three hours, results show low pressure readings the tests will stop, Allen said Wednesday night. If the cap shows high pressure readings for up to 48 hours than the cap could be used to completely shut-in the well, Allen said.

If not, the BP said it would hook the cap up to several containment vessels that could capture nearly all of the oil flowing from the well. It is estimated that up to 60,000 barrels of oil a day are spewing from it. However, the company and government are ultimately relying on the completion of a relief well, which has been delayed a "couple of days," by the tests, Well said. BP has said the relief well could be finished by the end of July, while the government estimates it will be completed in August.

No matter the determination on the well's fitness, BP said the cap's installation was an important step for spill responders working to prepare for an expected busy hurricane season. The new cap can allow containment vessels to more quickly disconnect from the system and flee a storm.

For the past several weeks, a more loosely fitting cap and the Q4000 system have managed to keep up to about 25,000 barrels of oil a day out of the Gulf.

The new sealing cap system, plus additional measures, could allow the recovery of 60,000 barrels to 80,000 barrels by the end of the month, BP has said.

On Wednesday, BP collected about 12,800 barrels of oil from the well, Wells said. The number was lower than usual because BP had to disconnect the two containment vessels, the Q4000 and Helix Producer, in order to begin the procedures for the well test. However, once the test was delayed, those two ships were brought back online overnight, Wells said.

Together they are now processing at a rate of about 22,500 a day. The two vessels will disconnect again if the integrity test starts.

Διαβάστε ακόμα