The incident took place on February 21, but the mystery behind the two missing children was uncovered only on March 3, when one of them was found lying in Sion hospital.

Police said at around 1.30 pm on February 21, the accused, Gandamma Maitress, took her step-sons Akash (8) and Avinash (5) to a dilapidated and abandoned building (no 144) inside the Central Government Staff (CGS) quarters, Antop Hill, under the pretext of collecting trash. Once on the terrace of the building, she beat the two and hurled them on to the ground a good 48 feet below, police added.

While Avinash was admitted to LMT Hospital, Sion, the same day after some locals found him lying unconscious next to two pipes near building 144, the decomposed body of Akash was found three days later on the right side of the building. Akash'sbody could not be found earlier because he lay amid a cluster of abandoned buildings which have been declared unsafe by the government. Moreover, there is no road on the right side of the building.

The father of the children, Ravindra, had lodged a complaint with Antop Hill police station on February 21 that the two were missing. Gandamma had then told him she did not know where they had gone since afternoon.

Police found Avinash at Sion Hospital on Wednesday, after which the truth was bared. Senior inspector Praladh Shinde said Gandamma was arrested after Avinash told police that she had beaten him and Akash before pushing them off the terrace. The motive, however, is yet to be established, Shinde added.

``Avinash was too frightened to speak. It was an arduous task recording his statement,'' Shinde pointed out. Police said the five-year-old is still in a state of shock. Moreover, he has been partially paralysed by the impact of the fall.

A post-mortem report has revealed that Akash's death was causedby skull fracture. He also suffered multiple damage of the torso, police added.

It is still not clear if Gandamma was married to Ravindra, but investigations have revealed the couple were staying together in the nearby slums for the last 18 months.

A metropolitan magistrate at Kurla today remanded Gandamma to police custody till March 15.