Deputy Commissioner of Dhaka Metropolitan Police (north zone) Golam Rasul described it as just another accident and told The Daily Star police were investigating the case.

Six days into the tragedy that reduced four next-door families to an emotional wreck, the outcome of the probe is still unknown -- an indication investigators may let it slip beyond people's concern like other nerve-wrecking cases.

Relatives of the dead and locals of Faidabad neighbourhood in Uttara believe an unknown person drowned the children into the 15 feet by 15 feet water tank, as the bodies they say did not bear hallmarks of injury commonly suffered in an accident.

A violent shock convulsed the parents of Sonia, 7, her brother Jamil, 1 year and 3 months, Mahmuda, 4 years and 6 months, Tamanna, 5, and Russell, 6, found dead in the four feet deep water.

Like other days, the children came out of their houses -- all before 10:00am -- after breakfast with their parents or sisters.

"I saw them playing when I went out for work," said Mujibar Rahman, father of Sonia and Jamil -- face registering numbing shock.

His wife Zayeda, disconsolate with grief, cried all day -- "My children, my children" and paced around in her room in desperation to forget the forlorn world she had woken up to.

"The loss is so great in so short time," said Jayeda who also lost her 13-year-old mentally challenged daughter Masuma Akhtar Moni three months ago.

"We were bringing them up with great care. We did not imagine we had this in store for us," said the mother strangling a sob and hugging 11-year-old Zahid, her only living child.

The parents carried out hectic searches in the neighbourhood, as they found none of their children even after they announced lost-child calls on loudspeakers about an hour.

Mahmuda's mother Monwara Begum fainted on hearing the news and is still reeling from trauma -- all by herself as her husband Sharif Uddin and most of her close relatives live in Saudi Arabia.

"I heard someone screaming a man kidnapped five children and people are looking for them," said Russell's aunt Sabina, bursting into sharp wails of grief.

Although most relatives resigned themselves to the belief that it was an accidental death, Russell's mother Sheuly Begum's suspicion is other way round.

"How could all drown without raising alarm for help?" she asked.

Russell's uncle Badsha Miah says it is all but impossible to ease into the tank as it has a metal cover of 13 inches in diameter, adding: "One has to jump with hands up or put pressure to get into it."

It is also suspected that the children might have dropped to death when they peered into the tank opening its lid and suffered suffocation from toxic gas that some residents believe formed inside.

But Jayeda ruled out the possibility of toxicity and said: "I used to collect water from the tank when there was no supply to my home."

Star City found neighbours peeking into the reservoir but they were unharmed by any gas poising.

Some locals linked the death of the five to a feud over property between Mujibar and his relative Imran who owns the under-construction building housing the tank.

They claimed to have seen Imran telling police and others that the children plunged to death in the tank and said he initiated the search for the children.

The cover of the tank is open and hundreds still gather there to peer into the dark of the reservoir that proved a death trap.