Nine people were killed in the blast in Maryhill

A hearing at the High Court in Glasgow was told that the blast happened after petroleum gas ignited in a pipe which had been corroding over the years.

The companies which owned Stockline face four charges brought under the Health and Safety at Work Act.

Their trial, expected to last 12 days, is due to get under way next month.

Defence QC Paul McBride told a preliminary hearing on Tuesday that discussions with the prosecution could have a "significant impact" on the trial and could reduce its duration even further.

He also revealed that a huge amount of technical evidence had been agreed.

The cause of the explosion was the ignition of petroleum gas in a pipeline which over the years had corroded Angus Stewart QC Prosecuting

He said that relatives of the nine dead and 24 injured in the blast on 11 May, 2004, in Maryhill, would not have to give evidence "about the tragic circumstances of that day".

The trial of the two companies which owned the business, ICL Tech Limited and ICL Plastics Limited, is due to start on 13 August.

They face charges alleging that the companies failed to ensure their workers were not exposed to risks of personal injury and death from fire, explosion and other dangers arising out of corroded pipes and an escape of liquid petroleum gas which accumulated in the basement and exploded.

Angus Stewart QC, prosecuting, said the exact cause of the explosion had been agreed between the Crown and the defence.