After a two-day joint inquiry into the deaths of shop assistant Ng Yong Soon, 25, and his elder sister, Ms Ng Li Hua, 26, a clerk, last Sept 13, State Coroner Victor Yeo recorded an open verdict on Tuesday.

The two siblings lived with their parents on the third-floor of Block 683 Hougang Avenue 8.

The fire had apparently started at a minimart three floors directly below their home. It had stored a variety of mid-autumn festival goodies in a makeshift rectangular canvas enclosure.

Two overhead lanterns were found burning.

The caretaker had tried to put out the lanterns by stamping on them but the fire spread and grew bigger.

He had earlier heard the voices of two teens talking and a third teen laughing.

He also heard the sound of an aluminium cover that encased the mobile ice-cream fridge being lifted.

He shouted but there was no response.

Another witness, Mr Ang Lye Kim, 34, was driving past the driveway of the minimart when a male teen dashed out of the aisle between the tarpaulin and the minimart. He was smoking and had dyed spiky hair.

Soon after, he saw four teenagers crossing the driveway.

Mr Ang was turning out of the carpark when he noticed caretaker Leow Hock Bee, 55, standing outside the makeshift canvas putting out a small fire.

Moments later, Mr Ang said the fire had grown huge and bright.

He also noticed Ms Ng walking out of the passage way at the back, looking dazed and badly burnt.

He alerted the police officers. Ms Ng was taken to hospital where she died about 16 hours later of severe burns.

Her brother's charred body was found at the foot of the block.

The two siblings had turned right after running out of the flat down the staircase into the heart of the raging fire. Their parents escaped by going the opposite direction.