Government investigators are now looking week to procedures by onshore managers for BP and Transocean that could have played a role in the oil rig disaster in the Gulf of Mexico.

After interviewing more than a dozen workers who live to tell the tale of the Deepwater Horizon explosion, a federal panel here is moving its attention to land-based supervisors from the two main companies operating aboard the rig.

Nguyen said that the master of the vessel, tasked with keeping a ship afloat, "should be the decision maker" and bear the ultimate responsibility. Generally drilling decisions, which can result in dangerous blowouts, are handled by offshore installation managers. The fact that ship captains don't have oversight over drilling "is one of the problems we have here," he said.

An onshore BP official, Neil Cramond, the marine authority for the Gulf of Mexico, testified Monday that at least 63 of the 70 repairs under his supervision had been completed by the day of the disaster.

But it remains unclear whether many of the most critical problems — including an “inhibited” safety alarm and broken watertight doors — were ever repaired. Another BP official reviewed the alarm system in March and found it operational, Mr. Cramond testified. But the rig’s chief technician, Mike Williams, testified last month that the main emergency alarm was not fully activated to avoid waking the crew with loud morning sirens.

Steve Gordon, a veteran maritime attorney who represents the rig's chief mechanic, Doug Brown, has long argued that maritime issues--such as engine maintenance and chain-of-command--deserve more attention from investigators.

He said that, "When a captain of a vessel testifies that he does not have the authority or the knowledge to activate the final safety function of a vessel, there's a problem.”