The Interior Department reprimanded an oil firm for repeatedly violating safety rules following a Gulf of Mexico explosion that left one worker dead and another missing.

Interior’s Bureau of Safety and Environmental Enforcement (BSEE) told Black Elk Energy that its offshore operations “must be improved immediately,” citing the firm’s previous safety violations in the Gulf of Mexico in its letter.

“Black Elk has repeatedly failed to operate in a manner that is consistent with federal regulations. BSEE has taken a number of enforcement actions, including issuing numerous Incidents of Non Compliance (INC’s), levying civil penalties and calling in the company’s senior leadership to review their performance and the ramifications of failing to improve,” BSEE Director James Watson said in a Wednesday statement.