Myriad agencies have investigated BP\'s Gulf of Mexico oil spill, but the owner of the rig that exploded and sank wants to draw the line at the one designated by Congress to probe disasters involving deadly chemical blasts and releases. The U.S. Chemical Safety Board, which investigates chemical explosions in the same manner the National Transportation Safety Board investigates airplane crashes, launched its first offshore investigation shortly after the 2010 explosion killed 11 workers and allowed more than 4 million barrels of crude to foul the gulf. However, Transocean Ltd, which owned the Deepwater Horizon rig, says the agency has no jurisdiction to obtain access to blast survivors, internal records and other information as other agencies investigate oil spills. The CSB also had never investigated offshore incidents before, the company argued. \"The magnitude may be unique, but there certainly have been ambient releases offshore,\" Transocean attorney David Baay said at a hearing before U.S. District Judge Lee Rosenthal in Houston on Thursday. Assistant U.S. Attorney Adam Goldman said the CSB has jurisdiction because its probe focuses on the blowout and explosion rather than the spill. \"The reason we\'re here is not because there was an oil spill. The reason we\'re here is that there was a loss of 11 lives,\" Goldman responded. Rosenthal was expected to rule at a later date. Don Holmstrom, the CSB\'s chief investigator in the case, told Reuters before the hearing that other companies involved with the Macondo well that blew out, including BP, Halliburton, Schlumberger and blowout preventer manufacturer Cameron International Corp were all cooperating with the agency\'s probe. Other spill investigations completed last year include a probe by the U.S. Coast Guard and the U.S. Interior Department, which put most of the blame on BP for the disaster. The CSB, created in 1990 and funded since 1998, has investigated chemical spills and refinery explosions, including the 2005 blast at BP\'s Texas City, Texas refinery that killed 15 people. The agency has no enforcement powers, but can recommend improvements in safety practices and regulations.