If the cap fits … waiting game for BP over oil spill

Engineers managed to fit a cap over the runaway well that has been gushing since early spring.

They will watch anxiously over the next day and a half to see if the 75-ton cap holds.

The accomplishment was greeted with hope, high expectations and, in many cases along the beleaguered US coastline, disbelief.

But BP chief operating officer Doug Suttles urged caution and warned the flow could resume. "It's far from the finish line. It's not the time to celebrate," he said.

However, no oil was flowing into the Gulf for the first time since an explosion on the BP-leased Deepwater Horizon rig killed 11 workers on April 20 and unleashed the spill 5,000ft beneath the surface.

For now, engineers and scientists are monitoring the cap for pressure changes around the clock. High pressure is good because it shows there is only a single leak. Low pressure could mean more leaks further down in the well.

President Barack Obama called the development "a positive sign".

But Mr Obama, whose political standing has taken a hit because of the spill and accusations of government inaction, cautioned that "we're still in the testing phase".

The worst case would be if the oil forced down into the bedrock ruptured the seafloor irreparably.

There is also always the possibility of another explosion, either from too much pressure or a previously unknown, unstable piece of piping.

It is not clear yet whether the oil will remain bottled in the cap, or if BP will choose to use the new device to funnel the crude into four ships on the surface.