CHENNAI: A 51-year-old woman and her 18-month-old grandchild riding pillion in a motorbike were killed after an over-speeding bike knocked their two-wheeler near Tirumazhisai in Tiruvallur district on Tuesday.

The deceased were identified as Anbarasi and Nihashri. Their relative, Anbazhagan, was riding the bike.

Police said that the child had fallen sick last week after which her mother, Revathy and grandmother, Anbarasi, took her to various hospitals in and around their residence in Sriperumbudur. Since her health had not improved, Anbarasi decided to take her to the Institute of Child Health and Hospital for Children at Egmore and sought the help of a relative, Dhandapani, to drop them there.

When the bike crossed Tirumazhisai, an over-speeding biker hit them from behind, and fled the scene. All three were thrown from the vehicle on impact. Passerby rushed to their rescue and moved them to nearby hospitals where Anbarasi and Nihasri died without responding to treatment.

The Avadi traffic investigation wing has registered a case of causing death due to negligence and rash driving, and has launched a hunt for the biker. Police have recovered CCTV footage in which the biker was seen brushing the deceased’s two-wheeler and fleeing the scene.