The union representing Health and Safety Executive (HSE) staff has called for a public inquiry into the Stockline factory blast in Glasgow.
An aerial photograph of the Stockline factory from the HSE
Nine people died and 33 people were injured in the incident in May 2004.
Owners and operators ICL plastics and ICL Tech were fined £400,000 for health and safety breaches.
The union Prospect supported calls for a full public inquiry and said it was disappointed by rumours casting blame on individual inspectors.
Michael Macdonald, Prospect negotiations' officer, said the prosecution had left many questions unanswered.
"The debate over Stockline should not scapegoat individuals constrained by public policy but should concentrate on improving the effectiveness of the HSE," he said.
Mr Macdonald said the inquiry should inform any changes needed to ensure the best health and safety protection for workers.
Earlier this month, the First Minister Alex Salmond said there was widespread support for a public inquiry.
The Lord Advocate Elish Angiolini is consulting the families and authorities involved and is expected to reach a decision by the end of the month.