A woman and her two-and-half year-old son were killed after an under-construction pillar of the "Namma Metro" (Bengaluru Metro) on Outer Ring Road near HBR Layout here collapsed, police said on Tuesday.

According to police, the incident took place around 11 am, when the TMT bars erected for the construction of a pillar fell on their scooter. The height of the pillar is said to be over 40 feet and weighing several tonnes.