Executives from BP PLC and the other companies involved in last year's drilling rig explosion and oil spill in the Gulf of Mexico are set to testify on Capitol Hill today after the House Natural Resources Committee expanded the scope of its hearing about a federal probe into the disaster.

The executives' testimony comes a day after the Interior Department issued seven violations to BP and four each to Transocean Ltd. and Halliburton Co. based on the findings of that probe.

Republicans on the committee and the Obama administration have been at odds for weeks about the witness list for the hearing, which will focus on the joint U.S. Coast Guard and Bureau of Ocean Energy Management, Regulation and Enforcement investigation into the disaster. Chairman Doc Hastings (R-Wash.) insisted on hearing from the men who led the investigation and postponed the hearing twice before he made a deal with the administration that allowed the investigators to testify along with higher-up officials at the two agencies.

This week, the committee said it would also hear from executives at BP, Halliburton and Transocean to discuss the findings of the probe, which were especially harsh toward BP.

BP America Vice President Ray Dempsey, Halliburton subsidiary Sperry Drilling Vice President James Bement, and Transocean's North American managing director Bill Ambrose will join the federal investigators -- U.S. Coast Guard Capt. Hung Nguyen and former BOEMRE employee David Dykes -- as well as Coast Guard Vice Adm. Brian Salerno and Bureau of Safety and Environmental Enforcement Director Michael Bromwich in testifying before the committee.

Tensions will likely run high at the hearing as the companies are embroiled in numerous lawsuits about the disaster and could face billions of dollars in fines for their role in the accident that launched the nation's worst oil spill. But a Republican aide said GOP lawmakers will remain focused on the findings of the probe. The investigation team last month released a 212-page report, which blames much of the 2010 oil spill disaster on poor management decisions by BP and makes a series of regulatory recommendations to improve the safety of offshore drilling.

The federal citations issued yesterday are also likely to crop up in today's discussions.

The Bureau of Safety and Environmental Enforcement accused the companies of failing to keep the well under control, not performing work in a safe manner and discharging pollutants into offshore waters, among others issues. And the citations could result in millions of dollars in fines for the companies.

Yesterday's violations issued by BSEE are separate from other penalties that the companies will likely face under the Clean Water Act. Those fines could top $21 billion for BP, based on current discharge estimates.

Democrats could also raise other issues at the hearing. Rep. Ed Markey (D-Mass.), the ranking member on the panel, is sure to bring up his request for the top executives at the companies to testify before Congress. Since last fall, Markey has been involved in a battle of wills with BP CEO Robert Dudley, who refused to testify until his company had time to digest the recommendations of the president's oil spill commission, which released its report in January.

Democrats lost control of the chamber in January, and since then, Markey has urged his Republican colleagues to summon the BP executives to Capitol Hill.

Yesterday, he said the presence of Dempsey, Bement and Ambrose does not go far enough.

"I requested that the CEOs of those companies testify. I think that would give us a keener insight into what in fact transpired back in 2010 and what the pathway has been to the conditions that we see today," he said in a brief interview. "I think the CEOs should testify, and if not at this hearing tomorrow then at some such hearing in the near future."

Moratorium effects

Markey's comments yesterday came on the heels of a separate Natural Resources Committee hearing about the effects of the Obama administration's moratorium on deepwater drilling in the Gulf of Mexico, which was lifted one year ago yesterday.

That hearing resulted in name-calling from both sides of the aisle, as Republicans blasted the Obama administration for dragging its feet in issuing offshore drilling permits.

"While I recognize that some permits indeed are being issued, there are facts and data that demonstrate recovery is moving at a pace that continues to hamper job creation and the economy," Hastings said.

A bevy of Gulf Coast business leaders backed up Hastings' claims yesterday at the hearing, telling lawmakers that a slow permitting pace is affecting coastal companies across the board.

The Interior Department has issued 81 permits for new shallow water wells since new safety and environmental requirements were instituted last June. The agency has approved 41 new deepwater wells since February, when the industry unveiled its oil spill containment and capture technology -- a new requirement for drilling in deep waters.

But Hastings said those figures are not up to pre-spill levels and blamed the administration for the tough times communities on the Gulf Coast are facing.

"The livelihood of communities and businesses throughout the Gulf depend on safe and responsible offshore energy production," Hastings said. "It's been a year and a half since the Deepwater Horizon incident, and a year since the president's moratorium was officially lifted. It's time to get people back to work and get the Gulf's economy growing again."

Markey, on the other hand, blasted Republicans for focusing the hearing on what he called a "temporary pause" rather than the long-term environmental effects of the disaster.

"Holding a hearing on the impact of a safety check following an unimaginable oil spill is a little like holding a hearing on the impact of wearing a cast after shattering your leg, without looking at the accident that required the cast," Markey said.