A series of internal investigations over the past decade warned senior BP managers that the oil company repeatedly disregarded safety and environmental rules and risked a serious accident if it did not change its ways.

The confidential inquiries, which have not previously been made public, focused on a rash of problems at BP's Alaska oil-drilling operations. They described instances in which management flouted safety by neglecting aging equipment, pressured employees not to report problems and cut short or delayed inspections to reduce production costs.

Similar themes about BP operations elsewhere were sounded in interviews with former employees, in lawsuits and little-noticed state inquiries, and in e-mails obtained by ProPublica.

Tony Hayward has committed himself to reform since becoming BP's chief executive officer in 2007. Under him, the company has worked to implement an operating safety system to create "responsible operations at every BP operation," said Toby Odone, a company spokesman. BP has used the system at 80 percent of its operations and expects to bring it to the rest by the end of the year, he said.

Odone said the notion that BP has ongoing problems addressing worker concerns is "essentially groundless."

Because of its string of accidents before the April 20 blowout in the Gulf of Mexico, BP faced a possible ban on its federal contracting and on new U.S. drilling leases, several senior former Environmental Protection Agency department officials told ProPublica. That inquiry has taken on new significance in light of the oil spill in the gulf.

The reports detailing the firm's Alaska investigations -- conducted by outside lawyers and an internal BP committee in 2001, 2004 and 2007 -- were provided to ProPublica by a person close to the company who thinks it has not done enough to fix its shortcomings.

A 2001 report noted that BP had neglected key equipment needed for an emergency shutdown, including safety shutoff valves and gas and fire detectors similar to those that could have helped prevent the fire and explosion on the Deepwater Horizon rig in the gulf.

A 2004 inquiry found a pattern of the company intimidating workers who raised safety or environmental concerns. It said managers shaved maintenance costs by using aging equipment for as long as possible. Accidents resulted, including the 200,000-gallon Prudhoe Bay pipeline spill in 2006, which was blamed on a corroded pipeline.

'Disconnect'

Since the late 1960s, BP has pulled oil from under Alaska, usually without problems. But when it pleaded guilty in 1999 to illegal dumping at an offshore drilling field there, it drew fresh scrutiny and set off a cycle of attempted -- and seemingly failed -- reforms that continued over the next decade.

To avoid having its Alaska division debarred -- the official term for a contract cancellation with the federal government -- the firm agreed to a five-year probationary plan with the EPA. BP would reorganize its environmental management, establish protections for employees who speak out about safety issues, and change its approach to risk and regulatory compliance.

Less than a year later, employees complained to an independent arbitrator that the company was letting equipment and critical safety systems languish at its Greater Prudhoe Bay drilling field. BP hired independent experts to investigate.

The panel identified systemic problems in maintenance and inspections and warned BP that it faced a "fundamental culture of mistrust" by its workers.

"There is a disconnect between GPB management's stated commitment to safety and the perception of that commitment," the experts said in their 2001 report.

The report said that "unacceptable" maintenance backlogs ballooned as BP tried to sustain North Slope profits despite declining production. The consultants concluded that the company had neglected to clean and check valves, shutdown mechanisms and detection devices essential to preventing explosions.

In May 2002, Alaska state regulators warned BP that it had failed to maintain its pipelines. Alaska struggled for two years to make the firm comply with state laws and clear the pipeline of sedimentation that could interfere with leak detection.

Soon after, BP hired another team of outside investigators to look into worker complaints on the North Slope. The resulting 2004 study by the law firm Vinson & Elkins warned that pipeline corrosion endangered operations.

Two years later, in March 2006, disaster struck. More than 200,000 gallons of oil spilled from a corroded hole in the Prudhoe Bay pipeline. Inspectors found that several miles of the steel pipe had corroded to dangerously thin levels.

Too good to be true?

As BP battled through the decade to avoid accidents in Alaska, another facility operating under a different business unit, BP West Coast Products, had similar problems.

For years, the subsidiary that refined and stored crude oil was allowed to inspect its own facilities for compliance with emission laws under the South Coast Air Quality Management District, the agency that regulates air quality in Los Angeles.

In 2002, inspectors with the management district thought BP's inspection results looked too good to be true. Between 1999 and 2002, BP's Carson Refinery had nearly perfect compliance, reporting no tank problems and making virtually no repairs. The district suspected that BP was falsifying its inspection reports and fabricating its compliance.

According to Joseph Panasiti, a lawyer for the management district, the agency had to get a search warrant to conduct inspections required by state law. When the regulators finally got in, they found equipment in a disturbing state of disrepair. According to a lawsuit the management district later filed against BP, inspectors discovered that some tanker seals had extensive tears, tank roofs had pervasive leaks and there were enough major defects to lead to thousands of violations.

"They had been sending us reports that showed 99 percent compliance, and we found about 80 percent noncompliance," Panasiti said.

The district sued BP for $319 million. After lengthy litigation, the firm agreed to pay more than $100 million without admitting guilt. Colin Reid, the plant's operations manager, later was promoted to a vice president position in the United Kingdom. He recently left BP and did not respond to requests for comment.

Among the safety equipment that BP was criticized for not having in place in its Alaska facilities, according to its own 2001 operational integrity report, were gas and fire detection sensors and emergency shutoff valves.

Now investigators are learning that similar sensors and their shutoff systems were not operating in the engine room of the Deepwater Horizon rig that exploded in the gulf.

In testimony before a Deepwater Horizon joint investigation panel in New Orleans last month, Deepwater mechanic Douglas Brown said that the backstop mechanism that should have prevented the engines from running wild apparently failed -- and so did the air-intake valves that were supposed to close if gas entered the engine room.

He said the engine room wasn't equipped with a gas alarm system that could have shut off the power.

Minutes later, the rig exploded in a ball of fire, killing 11 workers before sinking to the seafloor, where it left a gaping well pipe that continues to gush oil and gas.