BP says it has reinstalled a containment cap on its blown-out well in the Gulf of Mexico after an accident unleashed a torrent of oil.

BP was forced to remove the cap after an underwater robot bumped into the venting system.

Gas had risen through the vent that carried warm water down to prevent ice-like crystals from forming in the cap.

The cap has been partially containing the leaking oil and directing some of it to a surface ship.

The decision to remove the cap for repairs meant that oil was flowing unhindered into the ocean for about 10 hours on Wednesday.

Crude has been leaking at a rate of between 30,000 to 60,000 barrels per day, according to US scientists. The cap has been collecting roughly 16,000 barrels every 24 hours, BP says.

In a separate development, two workers involved in the clean-up operation died, Coast Guard Adm Thad Allen said.

One death, he said, appeared to have been a swimming pool-related accident, while the second one was an apparent suicide.

It was not immediately known when the deaths had occurred and which company either of the two victims had been working for.

Rig blast

The spill was caused by an explosion on the Deepwater Horizon drilling rig, which killed 11 workers.

At a press briefing in Washington, Adm Allen said BP had removed the containing cap after the underwater robot bumped into the venting system on Wednesday.

The "top hat" cap, which works by trapping leaking oil and then sending it up to a container ship, was removed for inspection after crews detected gas, he said.

"They indicated the problem was a remotely-operated vehicle had bumped into one of the vents," he said.

The slick has closed fishing grounds, killed hundreds of turtles and seabirds and dozens of dolphins and affected the coastlines of four US states.

Emergency workers and fishermen in Florida said the oil was now being washed ashore on Pensacola Beach.

"It's just a line of black all the way down the beach as far as you can see in both directions. It's ruined," said Pensacola fisherman Steve Anderson.