US oil industry regulators slapped BP, Transocean and Halliburton with regulatory violations notices Wednesday in what is expected to lead to massive fines associated with the deadly 2010 Gulf of Mexico oil spill. It was the first time that regulators issued the violation notice -- called an Incidents of Non-Compliance (INC) -- directly to a contractor that was not the well\'s operator. \"The decision reflects the severity of the incident, the findings of the joint investigation, as well as Secretary Ken Salazar and Director (Michael) Bromwich\'s commitment to holding all parties accountable,\" the Bureau of Safety and Environmental Enforcement said in a statement. The decision could strengthen BP\'s legal case for recovering some of the massive multi-billion dollar costs of the spill from Halliburton, which performed the cement job, and rig owner Transocean. It comes after the regulatory agency issued a report in September which spread the blame for the massive oil spill in the Gulf of Mexico, citing a bad cement job, poor management by BP and its subcontractors and risky shortcuts. The findings were largely in line with other investigations into the 2010 disaster but were the most detailed to date. The US Justice Department is also conducting a criminal investigation into the deadly disaster which killed 11 workers aboard Transocean\'s Deepwater Horizon drilling rig on April 20, 2010. By the time the well was capped 87 days later, 4.9 million barrels (206 million gallons) of oil had gushed out of the runaway well 5,000 feet (1,500 meters) below the surface of the Gulf of Mexico. BP, which leased the rig and was ultimately responsible for operations, has spent $40.7 billion on the biggest maritime oil spill in history and could still be liable for billions in fines, compensation and restoration costs.