A five-year-old who was accidentally locked inside his parents' eighth-floor Woodlands Close office was found dead at the foot of the building on Saturday.

Soo Jia He, who had been left alone for around 10 minutes according to his parents, is believed to have attempted to escape through a window.

Jia He's mother, who gave her name only as Ms Hu, told Shin Min Daily News: "Our home is only a five-minute drive from the office. I couldn't believe that when we rushed back to the office, we would see my son's body lying on the ground floor."

Ms Hu added that she noticed the office window was open when she returned to the scene.

She believed that her son could have fallen from the window in a panic, having witnessed their car driving away, a friend of the family told The Straits Times at the boy's wake yesterday.

The police said that they were alerted to a fall-from-height case at 11 Woodlands Close at about 9pm. The boy was found lying motionless at the foot of the building and was pronounced dead by paramedics at the scene.

The police are investigating the unnatural death.

Chinese-language newspaper Shin Min Daily News reported that the boy's parents had taken him and his brother to their office that day, and he had fallen asleep while they did some work.

The couple run an education centre, though there were no lessons held on Saturday.

When it was time to leave, the boy's father switched off the lights in the office and they drove home with his older brother.

It was only when the couple arrived at the carpark of their home that they realised they had left their younger son behind.

When ST visited the building yesterday afternoon, candles and joss sticks had been placed near the accident site - following a ritual the parents had commissioned for their son earlier that day.

The boy was the youngest of the couple's four children and he was doted on dearly by everyone, said the boy's father, who wanted to be known only as Mr Soo.

They have a daughter, who is in secondary school, and two other sons, the older of whom is 18. The other is in primary school.

"It is a tragic accident that nobody could have foreseen," Mr Soo told ST at the boy's wake yesterday. He said that both he and his wife have not slept since the accident the day before.

He said: "We don't know for sure how it happened, but all that does not matter now; the end result is still the same. Just like that, our son is gone. How are we going to be okay again?"