Published: Dec 07, 2010 8:00 PM EST
Updated: Dec 07, 2010 5:01 PM EST

HOUSTON (AP) - A technician responsible for monitoring gas levels told federal investigators Tuesday he never considered using his authority to stop work on the doomed Gulf of Mexico oil rig even though mud-moving activities in the hours before the blast made him uncomfortable.

Joseph Keith, who works for a unit of Halliburton, told the joint U.S. Coast Guard-Bureau of Ocean Energy Management, Regulation and Enforcement panel that the BP wellsite leader and mud engineers onboard would have been in a better position to assess whether work should have stopped.

"I just didn't think about it at the time," Keith said when asked why he didn't pull the plug on the job if he felt uncomfortable.

He said there was a lot of mud being moved around and other rig activities going on at the same time after he came on duty that evening. Previous testimony indicated workers had difficulty monitoring key data during a critical time in the final hour before the explosion because so many activities were happening at once.

The panel now appears to be honing in on that issue, asking pointed questions about why work on the rig wasn't halted.

The panel is nearing the final stretch in its quest to assign blame for the disaster.

This is the panel's sixth series of hearings, and at least one more is expected after this one before the panel issues its report, which is due by March 27. The panel is still awaiting the results of forensic testing on a key piece of evidence - the blowout preventer that failed to stop the spill. Investigators are analyzing it at a NASA facility in New Orleans.

On offshore drilling rigs, it is common to give all workers onboard, and even other passengers who may be laymen, the authority to stop work if they see an unsafe condition.

As a senior mud logger, Keith's duties involved using an assortment of electronic instruments to monitor the drill bit for traces of oil or gas and check for concentrations of hydrocarbons in the drilling mud, and notifying rig personnel when levels are too high. Hydrocarbons, a mixture of hydrogen and carbon, are found in crude oil.

Keith said that at some point he felt a vibration in a control panel, smelled gas, then a short time later heard a loud explosion. He headed for a lifeboat.

The explosion aboard the Deepwater Horizon on April 20 killed 11 men and led to more than 200 million gallons of oil spewing from BP's undersea well, according to the government's latest peer-reviewed tally. Roughly 34 million gallons were captured at the wellhead.

BP argues the government's estimate of how much oil was released is overstated. The amount of oil spilled is central to how much BP and other companies may be ordered to pay in fines.

Besides issuing conclusions on the cause of the explosion, the panel also was expected to make recommendations on how to improve regulation, safety and oversight.

Other federal agencies, commissions, members of Congress and the companies involved have been investigating. However, this panel's inquiry, which began in May, has been among the most exhaustive and has included sworn testimony from dozens of key officials, rig workers and contractors.

BP and Transocean officials also were expected to testify during this series of hearings, which began Tuesday and were to run through Thursday.

--- Online: Deepwater Horizon Joint Investigation: http://www.deepwaterinvestigation.com BP PLC: http://www.bp.com/

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