A decade ago, a mosquito breeding check by environment officers at an empty, dilapidated house in Upper Thomson led to a grisly find of a human skeleton lying on top of a toilet.
Fast forward to Sept 9 last year, and a worker clearing rubble from the guest room of the same house at 17 Jalan Batai in Sembawang Hills Estate discovered another set of bones - this time an adult human skull and a thigh bone.
Were these the remains of a pair of reclusive sisters, Madam Pearl Tan Leen Hee and Madam Ruby Tan, who had lived in the house?
There is no conclusive proof, said State Coroner Marvin Bay yesterday, but the circumstantial evidence does not point to anyone else living there, he added.
"Further, both sets of remains are notably those of elderly women, with the present set found to conform more closely to Madam Ruby Tan's chronological age," said the coroner. A pathologist had estimated that the latest set of remains belonged to someone who died at least a few years ago and was likely to be 60 to 70 years of age.
Madam Pearl Tan, a former civil servant, would have been 81 in 2006, when the first skeleton was found, and her sister, 68.
While the coroner excluded foul play, he could not say for certain what the cause of death was, for instance, misadventure or natural causes, in the latest case.
"Because of the very considerable time elapsed before the discovery of the second set of remains from the date of probable demise, as well as the reclusive manner that the two sisters lived their lives, eschewing social support and company of others, this case remains an enduring enigma," he added as he declared an open verdict.
The same decision was reached by another coroner in 2007 in the previous case.
Last year, a contractor was engaged by the Building and Construction Authority to clear debris such as discarded items and fallen-in roofing from the house. After the discovery of the skull, police uncovered other skeletal remains in the same guest room. Some of the bones were covered or buried in soil. Residents told the police then that they never heard any commotion or dispute in the house, and the sisters had not been seen for at least 10 years.
Madam Ruby Tan had suffered from schizophrenia, and had an outpatient treatment history with the Institute of Mental Health.
However, Madam Pearl Tan, who was last seen at the wedding of a relative in 1991, had $227,000 in bank deposits, and had last drawn from the account in 2004.
Investigations showed that she apparently left Singapore through the Woodlands Checkpoint on July 18, 2004, and nothing was ever recorded of her returning.
After the first inquest, a niece came forward. Madam Woon Sook Han, 56, had never met her aunts, but found out that their mother, Madam Wong Gek Lin, was the sister of her grandfather.
She applied to the Public Trustee's Office to administer the estate in 2013. The High Court issued an order last year that both sisters be presumed dead.