More than 40 people were injured in the Buncefield depot blast
Five companies are to be prosecuted over the Buncefield oil depot fire, the Environment Agency has said.
The huge explosion and blaze near Hemel Hempstead in Hertfordshire in December 2005 caused widespread damage and left 43 people injured.
The Environment Agency said criminal proceedings had now begun against Total UK, Hertfordshire Oil Storage and the British Pipeline Agency.
TAV Engineering and Motherwell Control Systems 2003 are also being prosecuted.
In a statement, the EA said the decision to prosecute followed "a thorough and complex criminal investigation conducted by the Health and Safety Executive and the Environment Agency".
The case is due to begin on 23 January at West Hertfordshire Magistrates Court in Watford.
Hertfordshire Oil Storage Ltd is the company which operated the Buncefield site. It faces two charges, including that it "failed to take all measures necessary to prevent major accidents".
The French owners of energy firm Total UK, which is a 60% shareholder of Hertfordshire Oil Storage, face three charges, including that they "failed to ensure, so far as is reasonably practicable, that persons not in their employment were not exposed to risks to their health or safety".
Both companies, along with the British Pipeline Agency, are also accused of polluting ground water supplies with fuel and other chemicals.
TAV Engineering and Motherwell Control Systems 2003 face one charge each of failing to adequately protect the health and safety of members of the public.
The Buncefield blast was the largest in Europe since the end of World War II.
Homeowners and businesses affected are currently embroiled in a legal bid for compensation at the High Court in London.