NEW ORLEANS – Engineers removed a temporary cap Thursday that stopped oil from gushing into the Gulf of Mexico from BP’s blown-out well in mid-July. No more oil was expected to leak into the sea, but crews were standing by with collection vessels just in case.

The cap was removed as a prelude to raising the massive piece of equipment underneath that failed to prevent the worst offshore oil spill in U.S. history.

The government wants to replace the failed blowout preventer first to deal with any pressure that is caused when a relief well BP has been drilling intersects the blown-out well.

When that intersection occurs sometime after Monday, BP is expected to use mud and cement to plug the blown-out well for good from the bottom.

As the cap was slowly removed at 5:25 p.m. Fort Wayne time, hours after a pipe latched to the top of it, there was no sight of anything spewing into the water. Undersea video feeds showed the cap suspended in the water. BP planned to place the cap on the seafloor nearby.

With the cap gone, the old blowout preventer can be removed and a new one put in place before engineers try to seal the well for good deep underground.

Once the blowout preventer is removed, a lot will be riding on the stability of a plug that was created when mud and cement were pumped down into the well from the top. Essentially, the pressure exerted downward served to counter the pressure coming up.

But Rice University engineering professor George Hirasaki said there is still uncertainty about whether the cement settled everywhere it needed to in order to keep oil and gas from finding its way up.

“Just because it didn’t flow when they tested it doesn’t mean the cement displaced all of the oil and gas,” Hirasaki said.

That’s why many people have felt that finishing a relief well and pumping mud and cement in through the bottom would be the ultimate solution to the crisis, Hirasaki said.

The government still plans on ordering BP PLC, the majority owner of the well, to do the “bottom kill” operation. But it believes the wisest course is to put on a new blowout preventer first to deal with any pressure that is caused when the relief well intersects the blown-out well.

Another potential risk: What happens if the crane attached to the blowout preventer accidentally drops the 50-foot, 300-ton device onto the wellhead? By itself, that might not cause more oil to spew, as long as the plug held, but it would make it difficult to continue the operation, Hirasaki said.

“It would crush everything,” he said. “It would be hard to place another blowout preventer on top of it. Right now the wellhead condition is in good condition. But if you dropped it, everything could be opened up.”