Before last week's fatal fire at one of Black Elk Energy's oil production platforms, the five-year-old firm had racked up more than 300 documented mistakes and violations offshore, according to federal regulators who cracked down on the Houston-based firm Wednesday.

The federal government ordered the company to immediately cease burning, welding and other activities that could ignite fires at all of its 98 oil and gas production facilities in the Gulf of Mexico. Regulators also are insisting on a third-party audit of Black Elk's safety management systems and are barring the company from launching work at facilities that are currently offline.

"Black Elk has repeatedly failed to operate in a manner that is consistent with federal regulations," said James Watson, director of the Bureau of Safety and Environmental Enforcement that oversees offshore oil operations.

The move came as federal investigators deepened their probe of what caused an explosion on Black Elk's West Delta 32 production platform last Friday, killing a worker, critically injuring others and leaving one still missing.

Black Elk's long history of violations offshore has been documented in 315 of what regulators call "incidents of non-compliance" issued by the safety bureau since 2010. On 12 separate occasions, it ordered the company to shut in its facilities because the violations were considered so severe or life threatening that work could not safely continue.

During that same two-year time frame, the safety bureau ordered Black Elk to shut off specific equipment 145 times because it was too risky to continue operating. The agency also issued 158 warnings to the company, ordering it to correct violations identified during inspections of Black Elk's facilities.

In one case two years ago, regulators ordered Black Elk to pay a $307,000 fine for violating testing requirements after the safety bureau determined the company had not tested a safety valve every six months as mandated. When it finally was tested, the valve was found to be leaking excessively - and then it took another 117 days to be repaired or replaced.

Although Black Elk was first formed in 2007, it has only been operating facilities in the Gulf of Mexico since 2010. In the past year, safety bureau officials have inspected Black Elk platforms 214 times and well operations on two dozen occasions.

"BSEE has taken a number of enforcement actions, including issuing numerous incidents of non compliance, levying civil penalties and calling in the company's senior leadership to review their performance and the ramifications of failing to improve," BSEE's Watson said. Wednesday's action "is an appropriate and necessary step as we continue to investigate the explosion and fire that resulted in the tragic loss of life and injuries last week."

Incidents of non-compliance can kick off a lengthy civil penalty process that can result in fines of up to $40,000 per incident per day.

BSEE detailed its requirements to Black Elk in a letter to the company Wednesday. It ordered the firm to submit a performance improvement plan detailing the steps it will take to ensure compliance in its operations. The agency threatened that if it doesn't see evidence of improved performance, the company could be barred from operating facilities on the outer continental shelf.

The safety bureau also asked Black Elk to prove how it had changed procedures and equipment in response to previous violations to prevent similar incidents on other facilities.

Black Elk's history of repeated violations - coming after the 2010 Deepwater Horizon disaster sparked major changes in the government's regulation of offshore drilling - raises fresh questions about the adequacy of the federal oversight. Some lawmakers on Capitol Hill have unsuccessfully pushed legislation that would bar companies with repeated violations from buying offshore drilling leases or working on the outer continental shelf altogether.

Federal regulators have some discretion to take action against companies operating offshore already, under the terms of the leases they hold with the government.

Black Elk's history and the platform fire appear certain to revive calls for stiffer punishments, but any big hike in the maximum fine or other new penalties would be up to Congress; otherwise, regulators can only raise the fine periodically to adjust for inflation.

Black Elk officials did not immediately respond to a request for comment.

According to safety bureau records, Black Elk was cited for an incident last Aug. 5 that sent two workers plunging 60 feet into the Gulf of Mexico while a crane was attempting to lower them in a personnel basket onto a boat. They weren't injured.

Regulators also investigated a fire on a Black Elk platform in February 2011 that was later traced to an improperly enclosed rechargeable battery.

Following last week's platform fire, a Coast Guard search was suspended late Sunday. Black Elk called off additional searches Tuesday evening, after one body was found.

Inspectors with the Bureau of Safety and Environmental Enforcement have been at the platform securing potential evidence, ensuring the site is safe and overseeing a cleanup of residual oil that could spill into the Gulf of Mexico.

The Chemical Safety Board, an independent federal agency that has investigated more than 50 industrial accidents, also has subpoenaed Black Elk Energy and Grand Isle Shipyard, the contractor working on the platform at the time of the fire, seeking combustible gas testing results, hot work permits, safety assessments and other documents.

Scrutiny has focused on the possibility that a torch ignited flammable materials on the site. Black Elk CEO John Hoffman said the explosion occurred during maintenance work at the site, when workers were cutting a water line. He said workers may have used a cutting torch instead of a saw, igniting flammable vapors in the line and subsequently triggering an explosion in connected oil tanks.

Activities that involve burning, welding or other operations capable of starting fires or explosions - called "hot work" in industry parlance - have been blamed for more than 60 deaths in the United States over the past two decades. Hot work has been a major factor in so many industrial accidents that the federal Chemical Safety Board has warned companies to monitor the amount of flammable gas in the atmosphere constantly before using burning, welding or other sparking tools.

Founded in 2007 by Hoffman, a former BP and Amoco executive, Black Elk holds interests in 854 wells connected to 155 platforms spanning the Gulf of Mexico. It is the main operator on 98 platforms, according to federal records.

As of 2011, Black Elk recorded estimated total proved oil and natural gas reserves of 45.2 million barrels of oil equivalent, mostly concentrated in the shallow waters of the Gulf.

Although the platform where the blaze ignited last week was not producing at the time, the company has estimated it is capable of producing about 600,000 barrels of oil equivalent per day.

The wells linked to the platform involved in Friday's accident date back decades to the 1950s and 1960s. Federal records indicate the company took over as operator at the offshore oil lease from Energy XXI GOM in 2011.