After reports that a BP "company man" overruled workers for the oil rig company Transocean on a key safety procedure prior to an explosion which set the rig aflame and sinking into the Gulf of Mexico, a senior BP official that was on the rig when it exploded has told investigators he will invoke his Fifth Amendment right not to testify in the case.

"One of BP's company men on the Deepwater Horizon when it exploded, Robert Kaluza, has declined to testify before the investigative panel in Kenner, citing his Fifth Amendment right not to incriminate himself, the Coast Guard said," according to the New Orleans Times Picayune. "Kaluza was scheduled to testify Thursday in the joint U.S. Coast Guard and Minerals Management Services hearings in Kenner."

The Louisiana paper also said a second BP official, Donald Vidrine, told the Coast Guard he couldn't testify Thursday because of "illness."

BP was leasing the oil rig from the multi-billion dollar oil company Transocean at the time of the blast. Transocean employees were managing its operation under BP's guidance. Transocean owns nearly half of the world's drilling rigs.

According to McClatchy Newspapers, BP won't even identify what role the two men had on the rig.

"BP wouldn't identify what role Kaluza and Vidrine had on the Deepwater Horizon," the paper's Washington bureau reports.

"Company spokesman Graham MacEwen said that any decision about whether to testify to the joint Coast Guard and Minerals Management Service inquiry would be up to those employees and their lawyers."

The BP officials' silence may bode poorly for the company if the case comes to prosecution for criminal malfeasance. Adds McClatchy:

Wednesday's government hearing in Louisiana, however, failed to determine why � despite unusual pressure and fluid readings on the rig � a BP official decided on the day of the explosion to proceed with removing heavy drilling fluid from the well and replacing it with lighter-weight seawater that was unable to prevent gas from surging to the surface and exploding.

Employees and experts testified that in the hours before the explosion, they witnessed a power struggle over that decision � the kind of argument common among the different parties that lease and run complicated offshore drilling operations, but one that this time, had deadly consequences.

One employee who worked for the rig owner, Transocean, was so mad after the fight that he warned they'd be relying on the rig's blowout preventer if they proceeded the way BP wanted.

"He pretty much grumbled, 'Well, I guess that's what we have those pinchers for,'" the rig's chief mechanic, Doug Brown, said of Jimmy Harrell, the top Transocean official on the rig. "Pinchers" was likely Harrell's reference to the shear rams in the blowout preventers, the final means of stopping an explosion.

Blame appears to be shifting in BP's direction from the drilling operator.

Carl Smith, a former U.S. Coast Guard captain and expert witness, testified Wednesday that the oil giant was ultimately responsible for ordering Transocean's workers around.

"Their emphasis is they're trying to drill to make money for their company, so their primary interest is to make progress on the well," Smith is quoted as saying. "So, you're always going to have a conflict between the people who are representing the owner's of the rig and the people who are renting it because the people who are renting it want to go faster and drill, and the people who are operating the rig want to maintain the integrity of the rig, which is a natural conflict."