Federal investigators examining what caused the Deepwater Horizon disaster are running into major roadblocks as drilling rig workers refuse to testify under oath about the incident and key stakeholders are questioning the inquisitors' jurisdiction. Although the Chemical Safety Board has successfully probed scores of other industrial accidents, including BP's Texas City refinery explosion in 2005, the independent federal agency's investigators say they are encountering an unprecedented array of obstacles in their Deepwater Horizon inquiry. 'In Texas City, there was some generally good cooperation from the regulator, from BP (and) from the various contractors,' said Don Holmstrom, the CSB's investigations manager. 'There was no delay in getting interviews' with refinery workers, and even a company-funded personal attorney encouraged the plant manager he was representing 'to communicate the full picture.' That isn't happening this time around, Holmstrom said. Instead, only one of eight Transocean employees subpoenaed by the CSB has been interviewed under oath, and another three have flatly refused to cooperate with the agency's investigation, Holmstrom said. Several lawyers representing individual Transocean employees have refused to accept subpoenas for their clients, even though some of the workers are now assigned to jobs outside the U.S. And a source familiar with the CSB investigation says that while most companies involved in drilling or sealing BP's doomed Macondo well have been cooperative, Transocean has increasingly put up resistance. The company also is challenging whether the CSB even has the authority to conduct its investigation. Transocean, which owned the Deepwater Horizon rig destroyed in the April 20 blast, insists it has cooperated with the CSB and, according to Brian Kennedy, a spokesman for Transocean, 'any assertion to the contrary is simply not true.' 'Transocean has voluntarily provided the CSB with volumes of information and is unaware of any unanswered or outstanding requests,' Kennedy said. 'The company has been cooperative with this and other federal agencies investigating the Macondo incident.' At least four major inquiries are under way into the lethal April 20 blowout of BP's Macondo well, which triggered the Deepwater Horizon rig explosion, killed 11 workers and unleashed an oil spill that dumped 4.9 million barrels of crude into the Gulf of Mexico. The Justice Department also is pursuing a criminal investigation. The CSB got involved in June at the request of House Energy and Commerce Committee Chairman Henry Waxman, D-Calif., who said he recognized that as an independent agency with no regulatory power, the safety board was 'in a unique position' to give an unbiased verdict on the incident. Unlike the CSB, other entities leading investigations, including the Coast Guard and the Bureau of Ocean Energy Management, Regulation and Enforcement, played a role in decisions about the well and oil spill response. But the safety board's authority to lead a Deepwater Horizon inquiry isn't completely clear -- a vulnerability that has been exploited by lawyers representing Transocean and its workers. In response to a CSB subpoena for records in August, Transocean stressed that it was voluntarily handing over the documents and insisted that the safety board didn't have jurisdiction. The company is prepared to go further, having drafted a legal filing obtained by Hearst Newspapers that would ask the Louisiana-based federal judge presiding over an oil spill lawsuit to rule that the Chemical Safety Board 'lacks jurisdiction to investigate the April 20, 2010 incident' and quash the CSB's subpoenas. Transocean's draft filing relies heavily on a provision in the federal law that created the safety board, which says the agency is not 'authorized to investigate marine oil spills.' There are different interpretations of the statute, and it has never been litigated. CSB officials stress they are investigating the Deepwater Horizon explosion itself, not the oil spill it triggered. They argue that the federal statute's ban on investigating any 'marine oil spill' refers to transportation-related spills, such as those from tankers. 'That's not the case here,' said CSB Managing Director Daniel Horowitz. 'This was functionally a fixed installation.' Although the Deepwater Horizon drilling rig was a mobile, floating vessel, at the time of the explosion, it was connected by a riser pipe to the blown-out well in the seabed. CSB insists that means both the well and the rig are stationary sources it has authority to investigate. But Transocean argues in its draft filing that the rig 'is still considered to be a vessel under way under maritime law' -- an assertion that would put it outside the safety board's reach. In refusing to comply with CSB subpoenas, lawyers for two of the rig workers also challenged the safety board's authority. Although the CSB could go to court and ask a judge to enforce the subpoenas, that is a risky move, because it would open up the jurisdiction question and could result in a ruling that turns against the agency. Transocean is paying for most of the attorneys representing individual rig workers. Attorneys stressed they are reluctant to allow their clients to talk to the CSB, because any written record of testimony can be used against a worker by criminal prosecutors later. Even a slight inconsistency between two sets of testimony might be used to threaten a witness with criminal charges, attorneys say. Attorneys add that if their clients must talk to investigators, they'd rather them give as few statements as possible and only talk to the officials that ultimately matter the most: criminal investigators. Many of the Transocean workers pursued by the CSB have already testified before the Coast Guard and the ocean energy bureau. One attorney said there's very little, if any, upside for his client to talk to the CSB. 'It's like when a telemarketing calls you at home,' the attorney said, who asked we not use his name out of concern that officials could respond negatively to his client. 'Why would you want to talk to a telemarketer if you don't have to?' Some attorneys have refused accept subpoenas on behalf of their clients. But in CSB's 20-year history investigating industrial accidents, Holmstrom said 'it's very unusual' to encounter attorneys unwilling to accept subpoenas for far-flung clients. The only other time the safety board encountered similar resistance, Holmstrom said, was during its 2001 investigation of a refinery fire in Delaware. Then, numerous supervisors subpoenaed by CSB did not show up for interviews, and their attorneys' arguments echoed each other. 'It's unusual for people to be saying the same thing' in fighting the subpoenas, Holmstrom said. 'It's almost unheard of.' Companies also regularly provide attorneys -- or pay for them -- to represent their workers after industrial accidents. Holmstrom notes that the safety board has interviewed witnesses in other accidents who were encouraged by the company-paid attorney 'to tell details of the incident that may not be flattering to the company' because they believe they are 'properly putting their client in the best light.' Regardless of who is paying the legal bills, an attorney is obligated to represent his client, said Charles Silver, a University of Texas law professor. The workers 'certainly have interests that are separate and apart from their employer,' Silver said. 'So the lawyer's obligation is to represent the employee' even if that isn't in the company's favor. Transocean affirmed that view. 'The express purpose of individual counsel is to protect and defend the rights of individuals,' the Transocean spokesman said. 'Decisions made by these attorneys and their respective clients are driven by just that.' (Jennifer A. Dlouhy can be reached at 202-263-6400 or at the e-mail address jdlouhy(a)hearstdc.com) 