Oil company BP will continue tests on its capped Gulf of Mexico oil well for an extra 24 hours.
The company expressed growing confidence that the ruptured well had been effectively capped.
Tests over a 48-hour period showed pressure was rising inside the cap, but is not as high as BP engineers initially hoped it would be, possibly due to the oil reservoir running dry.
If the pressure within the new cap on the well stays high, it could mean there are no other leaks or ruptures within the well bore. If it drops, that could suggest problems, the BBC reports.
BP is drilling a relief well which should intercept the leaking one at the end of July, enabling it to be sealed by mid-August.
The flow of oil was shut off at 2.25pm local time on Thursday. It was the first time BP managed to cap the flow since the explosion on 20 April that killed 11 workers.