A joint public inquiry into the Stockline factory blast in Glasgow is to be set up by the Scottish and UK governments, it has been announced.
The explosion claimed the lives of nine people
Nine people died in the 2004 explosion and 33 were injured.
Owners and operators ICL Plastics and ICL Tech were fined £400,000 for health and safety breaches.
Scotland's senior law officer, Lord Advocate Elish Angiolini, said a joint inquiry was the only way to properly address all the issues.
The factory blast, from which seven people were rescued, was caused by liquefied petroleum gas escaping from old and corroded pipe work.
The announcement of the inquiry came after a meeting between Ms Angiolini and UK Work and Pensions Secretary Peter Hain.
The full remit and timescale of the inquiry, the first in mainland Britain under 2005 legislation, will be finalised over the next few weeks.
It is expected to look into the events leading up to the explosion - including the role played by the Health and Safety Executive in its regulation of the premises - and the issues arising out of the incident.
Ms Angiolini, who earlier met relatives of the victims, said: "I am conscious of the anxiety that the families of those who died and the survivors have continued to suffer and both the secretary of state and I wish to ensure that the inquiry takes place as quickly as possible, and should not be unduly lengthy."
Mr Hain said he was "convinced", having met the families, that a full public inquiry was needed to understand what led to "this tragic accident".
"The families have suffered already and we do not want them to have to wait unduly for answers."
A memorial garden has been created for those who died
A spokesman for First Minister Alex Salmond said ministers were pleased at the announcement.
The decision was also welcomed by Patricia Ferguson and Ann McKechin, MSP and MP respectively for the area where the blast took place.
In a statement, they said: "This rewards the determined but dignified campaign conducted by the families over the last three years.
"We must make sure that we do everything possible to ensure never again will anyone lose their life because they went to work."
ICL said: "The companies welcome the inquiry and hope it will properly establish all the facts and circumstances relating to the disaster."
Scottish TUC general secretary Grahame Smith also welcomed the inquiry.
"We have worked closely with the families during this time and we are delighted that their determination to search for the truth has delivered the inquiry they wanted," he said.
"Hopefully, it will provide the answers to the questions that the families have been seeking as to how their loved ones died."