Federal investigators today issued a broad subpoena to Black Elk Energy in connection with the lethal fire Friday on one of the company’s oil platforms in the Gulf of Mexico. The Chemical Safety Board subpoena poses nine questions that could set the framework for a future inquiry into the incident, such as identification of witnesses and possible physical evidence on the platform. The CSB — an independent federal agency that has probed more than 50 industrial accidents, including the lethal Texas City refinery explosion in 2005 — also wants to know about the use of combustible gas detectors on the platform. That equipment, common on offshore facilities, can alert workers to the presence of flammable gas and may have played a role in Friday’s explosion, because construction contractors were apparently cutting through a water line at the time. Black Elk Energy CEO John Hoffman said the workers were set to perform a “clean cut” with a saw on that water line but may have used a cutting torch instead. If so, that may have ignited flammable vapors in the pipe, which was connected to wet oil tanks. The CSB also asked Black Elk Energy to turn over documents relating to safety and environmental management programs in use at the facility. Since November 2011, federal regulators have required offshore operators to employ “Safety and Environmental Management Systems” for boosting process safety and broadly identifying and mitigating risks. When federal regulators conducted their first audit of an operator’s SEMS program after that requirement went into effect last year, Black Elk Energy was the target. Federal investigators also want to know what substances were stored on Black Elk’s platform as well as information about the company’s track record. The Bureau of Safety and Environmental Enforcement can issue so-called “incidents of non compliance” to oil and gas companies — and contractors — operating on the outer continental shelf for violating offshore rules, with penalties of $40,000 per day per incident. Since the 2010 Gulf of Mexico oil spill, some lawmakers and regulators have argued that the fines need to be multiplied many times over and that companies with repeated violations should be barred from buying offshore drilling leases or working on the outer continental shelf altogether. Some lawmakers also have pushed for greater transparency about the enforcement actions taken against oil and gas companies operating offshore. Any big fine hike would be up to Congress; current law only allows the safety bureau to make periodic adjustments for cost of living. Federal regulators have investigated incidents at other Black Elk facilities in the Gulf. For instance, in August, there was a crane accident at one of the company’s facilities. In February 2011, a fire was ignited on a Black Elk platform and later traced to an improperly enclosed rechargeable battery. Daniel Horowitz, managing director of the CSB, said the agency had not yet made a decision about whether it would launch an investigation of Friday’s fire. The Chemical Safety Board has traditionally investigated industrial accidents — including other incidents involving the ignition of flammable and hazardous materials. It also is conducting an inquiry into the Deepwater Horizon explosion in 2010 that killed 11 workers and unleashed the nation’s worst oil spill, though rig owner Transocean has challenged the agency’s authority to probe the disaster.