The delayed early findings of an investigation into the Buncefield oil depot blasts are to be revealed later.
Causes of the Buncefield depot fire are being investigated
The inquiry aims to find the cause and environmental impact of the blasts and provide guidance for similar UK sites.
It has been described as the "most wide-ranging" of its kind since the Potters Bar rail crash inquiry in 2002.
A series of fires destroyed the depot in Hemel Hempstead, Hertfordshire, leading to the evacuation of homes and damage to nearby buildings in December.
Lord Newton of Braintree is chairing the inquiry, which was ordered jointly by the Health and Safety Executive and the Environment Agency.
He is joined by Prof Dougal Drysdale, an authority on fire safety, and Dr Peter Baxter, a medical expert.
Environment Agency and HSE staff are also on the board.
In December, Bill Callaghan, chairman of the Health and Safety Commission, said the inquiry would be the most wide-ranging of its type since the 2002 Potters Bar investigation.
The inquiry will consider the factors leading up to the 11 December blast, what ignited it and the root causes.