The Stardust inquests have heard the "probable" cause of the fire was either "electrical" or "deliberate".
Dr Will Hutchinson also told the proceedings that the most likely scenario is that the fire originated either in a hot press or in the partitioned-off seating area known as the west alcove.
This was Dr Hutchinson's second day in the witness box. A fire expert with over 20 years experience, he has been retained by the coroner’s legal team to give his opinions on the outbreak of the blaze.
He said he was unable to determine with any certainty the exact location of where the fire started, but said it was "possible" and the most likely scenario that it originated in the hot press in the main bar or started in the partitioned-off seated area known as the west alcove - where the fire was first seen by those inside.
He put the level of certainty as "probable" that it was caused by an electrical fault in the hot press, and said it was "probable" too that it was started deliberately in the west alcove.
The court heard how there were connection "issues" with the hot press. "Is this enough to cause a fire?" he asked. "Potentially, but we don’t know," he said.
He also told the jury that there were no witness accounts that would place anybody in the west alcove at the time of or immediately before the fire.
Ruled out
Dr Hutchinson said he has considered and ruled out the fire starting in the lighting or ventilation systems, the store and lamp room, and in the roof space or in the roof itself.
Referring to evidence from witnesses who told the court that they saw flames coming from the roof of the Stardust at a time before the fire was first spotted inside the club, Dr Hutchinson said he "just cannot see" how a fire can be established and going through the roof before people inside would start to see it.
"I believe they’ve seen the things that they have seen, but there might be some discrepancy in precise timings," he said.
Earlier in this evidence today, he said his main difficulty with the suggestion that the fire started in the roof space was that there were so many electrical circuits for the lighting there, that if there had been a significant fire in that space, then the lights would have gone out. He also said there was no significant fire load or fuel in that space.
Dr Hutchinson also played a video recorded shortly after the fire by experts at a premises in England that recreated the conditions inside the nightclub when the fire took hold. He said it showed that within two minutes, all of the combustible materials were involved with temperatures reaching 1200 degrees centigrade.
The inquests continue tomorrow when it is expected Dr Hutchinson will answer questions from the legal teams representing families of the dead.
In total, 48 people, aged between 16 and 27, died when the fire swept through the Artane nightclub in the early hours of St Valentines Day 1981.
