It is the first time the flow has stopped since an explosion on the Deepwater Horizon rig on April 20 .

The well has been sealed with a cap as part of a test of its integrity that could last up to 48 hours.

US President Barack Obama said the development was a "positive sign" but noted that BP was still in the testing phase.

BP executive Kent Wells said the oil had been stopped at 14.25 local time and he was "excited" by the progress.

"It is very good to see no oil go into the Gulf of Mexico," said Mr Wells.

BP shares rose in New York trading on July 15 after the flow was stopped, having already performed well over the day. But it is stressing that even if no oil escapes for 48 hours, that will not mean the flow of oil and gas has been stopped permanently.

Doug Suttles, BP chief operating officer, emphasised that there was no reason for "celebration" yet, particularly for those in areas already damaged by oil.