Construction work has resumed on the site of Sir Robert McAlpine鈥檚 拢360m Southgate shopping centre in Bath after it was ravaged by fire last week.

Workers returned to the site on Thursday morning, but the area where the fire occurred remained isolated.

The Health and Safety Executive (HSE) confirmed that an inquiry into the cause of the blaze at the Multi Development UK site was continuing, although it confirmed that it already had a firm idea as to how the fire began. The safety body said it was also focusing on the management of fire risks and general fire precautions on the site.

Scores of people had to leave the building last Tuesday after a series of explosions rocked the huge retail development, initially believed to have been caused by a faulty tar heater that leaked hot asphalt and led to the explosion of several gas canisters.

A spokesperson for the HSE said: 鈥淲e will be reviewing investigation reports from the contractors and the fire service, and seeking to establish how the fire occurred.鈥�

The safety body added: 鈥淲e are keen to ensure that construction sites have effective arrangements for controlling the risk of fire on site and emergency fire plans to ensure that, in the event of an emergency, all persons on site can be evacuated effectively and can be accounted for.鈥�