The last of the prosecution witnesses in the Doha mall fire trial has given evidence on how the deadly blaze was ignited.

Nineteen people were killed in last May's Villaggio fire, including New Zealand two-year-old triplets Lillie, Jackson and Willsher Weekes, who were being looked after at the daycare facility, Gympanzee.

Overnight, a forensic expert from Qatar's Ministry of Interior explained to the court the technical details of how the fire started.

The unnamed fire investigator said it was his team's job to determine the cause and origin of the fire and how far it spread, Doha News reported.


His investigation began at 2pm on May 28, while the mall was still on fire, and continued for four days.

He told the court the fire started when the flammable components inside a fluorescent lightbulb in the Nike shop came into contact with the hot plastic of the insulators within the device.

A malfunction caused the temperature of the electric conductor to spike, burning the insulators, which fell in ashes onto boxes of sports equipment and igniting them.

The smoke, which contained toxic gases, quickly spread to neighbouring Gympanzee, with fire eventually damaging 31 shops, he said.

The investigator also reiterated that the type of light bulb in question, which had an aluminum coil inside rather than a more fire-resistant copper one, was one commonly found by fire experts to be a cause of fires in Qatar, the newspaper reported.

He did not see any water at the mall that could have come from any sprinklers until a day after the blaze when the sprinklers were turned on.

The trial will continue for the 10th time next week as defence attorneys call their witnesses to the stand, including three employees of the Ministry of Labour.

At least some of the seven defendants in the case, including two Gympanzee co-owners, four representatives of Villaggio and an employee of the Ministry of Business and Trade, were also expected to give evidence.


Last week, the triplets' father Martin Weekes said the biggest question he had was why the judge had not been presented with an independent report into the fire.

"To this day, we have been denied access to that report ... not only have we been denied access to it, it's not been presented to the court. The most scientific piece of evidence that's available has not been presented to the court," he said.

The families of the 13 children killed in the fire met with the attorney general in Qatar earlier this month saying they needed the report.

"All we know is that it's gone to the Cabinet in the country and recommendations from that reports are supposed to be improving the safety in the country. Nobody knows what the recommendations are."

The report was produced in one week, after which all evidence in the mall was destroyed, Mr Weekes said.