Two children, aged four and eight, were killed when the compound wall of their house at Kakkan Nagar in Arumbakkam collapsed on them on Thursday evening.
While their parents were inside their home, the children were playing outside.
On hearing a sound, the family members and neighbours rushed out to see the children caught under the debris of the compound wall.
The wall had developed cracks, residents said.
Police identified the victims as Muskan, 4, daughter of Fairoz, and Dayan, 8, son of Fairoz’s brother Ansar. While Muskan died on the spot, the boy succumbed to injuries at the Government Kilpauk Hospital.
A case has been registered by the Aminijikarai Police under Section 174 of the Code of Criminal Procedure for unnatural death, and an investigation is under way.