Over 450 cubic metres of concrete mixture was injected through a surface bore in Bowbazar through Monday but it was still not enough to fill the vacuum that has been created underneath Durga Pithuri Lane and Shyakra Para Lane that had led to the subsidence and cracks in 18 buildings in the area.

https://timesofindia.indiatimes.com/city/kolkata/long-wait-for-light-at-end-of-tunnel-in-kolkata/articleshow/70953507.cms

BACKGROUND INFO: What happened at Kolkata East-West line?

https://tunnelcontact.com/discussion/view/3739/india-overlooking-subsurface-layer-composition-might-have-led-to-kolkata-east-west-tunnel-bowbazar-mishap-experts