KEVIN McGILL
Associated Press

NEW ORLEANS (AP) — A federal appeals court in New Orleans has upheld a federal safety board’s right to investigate the role of Transocean Deepwater Drilling Corp. in the 2010 Gulf of Mexico oil disaster.

Transocean owned the Deepwater Horizon rig that was drilling for BP PLC at its Macondo well, about 50 miles off the Louisiana coast when an explosion killed 11 workers and led to the nation’s worst offshore oil spill.

The company had challenged the authority of the U.S. Chemical Safety and Hazard Investigation Board, often referred to as CSB, to do the investigation.

In a 2-1 decision Thursday, the 5th U.S. Circuit Court of Appeals upheld a lower court’s ruling that the board could investigate.

Transocean officials did not immediately respond to messages seeking comment.

The investigation had continued during the appeal. In June, the board issued a report citing multiple failures and improper testing of the rig’s blowout preventer as factors in the explosion and found fault with BP and Transocean.

In affirming the safety board’s authority to investigate the accident, the 5th Circuit noted that the law gives the board power to look into the accidental release of hazardous materials into the air from a “stationary source.”

Transocean contended that the Deepwater Horizon, a portable rig that was moved from well site to well site, was a vessel under the law and not a “stationary source.” The courts, however, decided that the rig was a stationary source under the provisions of the Clean Air Act. “In this case, the Deepwater Horizon was deployed to the Macondo well site in February 2010 and had remained in place at the site for approximately two months,” Judge Thomas Reavley wrote in an opinion joined by Judge James Graves.

Judge Edith Jones dissented.

“This is the first time, in twenty years after CSB was ordained, that the agency has sought to investigate in connection with an offshore oil spill,” Jones wrote. “The majority’s interpretation of the Clean Air Act disregards the plain meaning of words and grammar and the most fundamental maritime concept, which is the definition of a vessel.”

Last year, while the appeal was pending, the 5th Circuit had refused Transocean’s request that it temporarily block enforcement of subpoenas of material sought by the safety board. The subpoenaed materials were eventually turned over, CSB spokesman Daniel Horowitz said in an email. “Unfortunately, the extensive judicial challenges have meant that we couldn’t effectively pursue all the witness interviews that we typically would have in a major case,” Horwitz said.

“With this decision, there is a clear path to completing the investigation in the first part of next year,” he added.

Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.