NEW YORK (CNN) -- Internal BP documents reveal the oil company's knowledge of "significant safety problems at the Texas City refinery," months or years before the March 2005 explosion that killed 15 workers and injured more than 170 others, according to preliminary findings released Monday by the U.S. Chemical Safety Board.

BP (Charts) has accepted full responsibility for the disaster at its plant and has settled more than 1,000 lawsuits related to claims made by those injured on site, by family members of those who died, and by people who suffered shock.

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More than $1.6 billion was set aside by BP to resolve those claims, a BP spokesman told CNN.

The CSB report says the company was warned of potentially hazardous conditions at the plant, and while it improved working conditions, "unsafe and antiquated equipment designs were left in place, and unacceptable deficiencies in preventative maintenance were tolerated," CSB Chairman Carolyn Merritt said.

Responding to the report, a BP spokesman said, "We agree with the CSB in that we, too, believe that the March 23, 2005, explosion was a preventable tragedy. However, we do not understand the basis of some of the comments made by the CSB board members."

The report reveals that between 1994 and 2005, there were eight incidents at the Texas City refinery that signaled grave problems. Two of those incidents involved fires, the report says.

Don Holmstrom, the CSB investigator leading the inquiry, said BP's efforts to improve safety at the plant in 2004 "focused largely on improving personnel safety - such as slips, trips and falls - rather than management systems, equipment design, and preventative maintenance programs to help prevent the growing risk of major process accidents."

Federal investigators have already fined the company $21 million for more than 300 safety violations at the plant.

"We are deeply sorry for what happened and the suffering caused by our mistakes," a BP spokesman said.

With one exception, all plaintiffs who filed claims against BP related to workers' deaths have settled with BP. The exception is Eva Rowe, daughter of Linda and James Rowe, who both died in the fire.

Rowe's case against BP is set to begin next week with jury selection in a Galveston, Texas, courtroom.

The Texas City refinery explosion was the worst industrial accident in the United States in more than a decade.

The news came as oil companies such as BP, ExxonMobil (Charts) and ConocoPhillips (Charts) face increased scrutiny over their operations in light of historically high oil and gasoline prices.

BP also was widely criticized after it was forced to shut down its Prudhoe Bay oil field in Alaska's North Slope last summer following a 5,000-barrel spill in the same field in March - the largest ever in the North Slope. Tests revealed severe corrosion in transit pipelines in the field.

BP is also under investigation for alleged manipulation of some energy markets.

-- from CNN's Katy Byron; CNN's Justin O'Kelly in London contributed to this report

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