A report last year by the Chemical Safety Board concluded that the blowout preventer’s blind shear ram, an emergency hydraulic device with two cutting blades, punctured the pipe and sent oil and gas gushing to the surface. The study found that the drill pipe had buckled under the tremendous pressure of the oil and gas rising from the well from the initial blowout.

That report warned that another disastrous offshore oil well blowout could happen despite regulatory improvements in the four years since the BP well explosion.

“The new regulation is important,” said William K. Reilly, a co-chairman of the presidential panel that investigated the spill, and the administrator of the Environmental Protection Agency under the first President George Bush. “The signal from the department that it is attending to each of the systems is more important. The blowout preventer is the last-ditch preventer. It was activated too late in Macondo. If you get to the point where it’s all you’ve got, it better be good. But the system process we identified — attention to management, process design, adherence to the system — those are really vital long before you ever get to the point where you have an emergency.”

Mr. Reilly blamed Congress for some of the continued systemic problems, saying that lawmakers should have appropriated funds to increase programs for safety training and inspection.

Administration officials say that since the spill, the Interior Department has initiated the most aggressive and comprehensive offshore oil and gas regulation and oversight in history. The agency has nearly doubled the number of safety inspectors in the Gulf of Mexico, from 55 at the time of the spill to 92 today. After the accident, the Interior Department was restructured, separating the agency charged with overseeing safety from the one charged with overseeing the collection of revenue.

The agency has also put in place a requirement that any company performing deep-water drilling in the Gulf of Mexico must have access to containment dome technology — essentially, a dome that can be put over an exploded well to contain gushing oil. At least two ports in the Gulf of Mexico now store containment domes that can be used in emergencies.

While the oil industry typically opposes regulations, it has followed some of the recommendations made by the presidential panel. The big oil companies created and funded the Center for Offshore Safety, an institute intended to promote and disseminate best practices in drilling.

“The industry’s overall safety record was strong before Macondo, and the co-chairs of President Obama’s national spill commission were absolutely right when they said that offshore drilling is now even safer,” said Jack N. Gerard, president of the American Petroleum Institute, which lobbies for the oil industry. “We will continue to build on these achievements because our goal is zero accidents and zero spills.”