BP met another setback with its oil-containment efforts in the Gulf of Mexico on Wednesday, when it removed a cap that had been sucking oil from an underwater gusher to one of the two ships on the Gulf surface for inspection.

The operation of its oil containment cap system was suspended after an underwater remote-operated vehicle (ROV) collided with the cap, said U.S. Coast Guard Admiral Thad Allen, the U.S. national commander for the oil spill.

The ROV accidentally closed a vent on the cap, disrupting the system that funnels oil to the drillship Discoverer Enterprise, said Allen. But he said oil was not spilling "unconstrained" because it continued to flow through a second containment system to a drilling rig that was flaring it. BP also confirmed in a press release that it suspended the operation of the oil containment cap after a discharge of liquid was observed at about 8:45 a.m. Wednesday from a diverter valve on the drillship Discoverer Enterprise, which is on station over the leaking underwater well.

"As a precautionary measure, the lower marine riser package (LMRP) containment cap system, attached to the Discoverer Enterprise, has been moved off the Deepwater Horizon's failed blow-out preventer (BOP) to ensure the safety of operations and allow the unexpected release of liquids to be analysed," it said.

It is the third time in eight days the drillship has stopped collecting oil. Its operation was suspended on June 15 after a lightening caused a fire aboard the ship. It was stopped again on June 19 due to an equipment problem and the threat of lightning.

The drillship accounted for 62 percent of 27,090 barrels of oil BP collected from the well Tuesday, according to BP. The rest was burned aboard the Q4000 vessel.

Also on Wednesday, BP, in a bid to restore its image after the spill, said it had replaced its much-criticized chief executive Tony Hayward with U.S. national Bob Dudley as head of the company's Gulf oil spill response team.

Hayward has handed over management of the Gulf of Mexico oil spill to Dudley, managing director of BP, "effective immediately", BP said in a statement.

Under the new structure, BP's response activities, which are centered in the Unified Command with the Coast Guard in New Orleans, will report directly to Dudley, the statement said.

Dudley, who grew up in Mississippi, has a deep appreciation and affinity for the Gulf Coast, and believes deeply in BP's commitment to restore the region," said Hayward.

The new organization will be responsible for executing oil clean-up operations, coordinating with U.S. officials, implementing the 20 billion dollars third-party claim fund, and evaluating the spill's impact on the environment.