The US drilling safety agency has said it determined BP had failed to conduct an accurate pressure integrity test in one area of the well.
And in four different sections of the well, BP failed to suspend drilling operations at the Macondo when the safe drilling margin was not maintained, the agency said.
An explosion at the Deepwater Horizon rig on April 20, 2010, killed 11 people, and the well gushed oil into the ocean for 87 days, polluting the southern US shoreline and crippling the local tourism and fishing sectors.
By the time the well was capped, 4.9 million barrels of oil had spilled out of the runaway well 5,000 feet below the surface of the Gulf of Mexico.
In October the US government issued BP, Transocean - the Swiss owner and operator of the drilling rig - and US oil services group Halliburton with citations for violating oil industry regulations in what is expected to lead to massive fines.
BP - which leased the rig and was ultimately responsible for operations - has spent more than $40 billion on the disaster and could still be liable for billions in fines, compensation and restoration costs.