Investigators said the possible source was in a department that sold foam boxes and plastic containers. The area has been marked and sealed off to prevent it from being tampered with.
A 15-strong team of investigators began collecting evidence yesterday in areas of the massive 30-rai (4.8-hectare) site where the fire was no longer smouldering.
Seven of the nine people who were initially reported missing have been found safe, but two are still unaccounted for.
Firefighters are seeking the cooperation of owners of radio-controlled planes to take aerial photos of the site to detect where fires are still burning.
As of yesterday, smoke was still billowing from several sites where the huge building had stood.
About 350 firemen, including those mobilised from neighbouring provinces, are calling for additional supplies – including fireproof gloves and boots – to move away burning debris. Their job has been made all the more hazardous by unexploded gas cylinders.
The store’s management has set up several tents nearby to sell goods and fresh products to customers in an attempt to keep staff employed and customers supplied.
A large number of Thai and immigrant customers were reported to be buying goods from the makeshift store.
Products at other SuperCheap convenience stores around Phuket are also still available as supplies from the main fire-damaged store are being redirected.
Phuket Deputy Governor Charoen Thipphayaphongthada has been appointed the chairman of an ad hoc committee to deal with the disaster.