Yesterday's terrible tragedy in Mong Kok has sparked one of our city's biggest investigations into a fire. The possibility that an arsonist could be responsible for the blaze is shocking, but there is evidence to suggest that is what happened. If so, the culprit must be swiftly brought to justice. Few crimes arouse as much contempt and anger as a premeditated attack on property that imperils the lives of innocent people. Meanwhile our thoughts must be with the families who have lost loved ones and those injured or left homeless. Last night the toll stood at nine dead. In 1997, arson was responsible for 17 deaths in a Tsim Sha Tsui karaoke bar, where a restaurant had become a fire trap without proper safety measures. A year earlier, the Garley Building fire had claimed 41 lives, also prompting calls for greater safety. Sadly we are now facing the same issue again.

Roadside hawkers' stalls stocked with highly combustible goods - where yesterday's blaze started - can clearly be fire hazards, although the danger is often limited as they are in the open. But the stalls usually front old buildings such as subdivided tenements in narrow streets and lanes that become vulnerable to fire. Those in Fa Yuen Street, Mong Kok, proved no exception. That was a factor in the loss of life. So quickly did the blaze engulf the stalls and sweep into the stairwells of adjacent tenements that residents did not have time to escape to the roof. Firemen found the bodies of a number of victims on stairways.

The tragedy raises two issues. It could have been much worse given that so many people in the tenements live in crowded, subdivided living spaces, many of them illegal. Worryingly, four of the buildings affected have illegal structures subject to demolition orders. Indeed, community leaders say deaths might have been avoided if the government had acted on recommendations for tackling fire hazards in the buildings. And the fire might not have spread so quickly if safety in the street market after a fire nearby last year had been more effectively enforced. Chief Executive Donald Tsang Yam-kuen acknowledged that measures such as separating market stalls from old residential blocks, maintaining regulation space between them and limiting the amount of stock stored had failed and needed to be reviewed.