DMC Srikant Sarmokdam, whose name was found in the diary of the builder (already arrested), was taken into custody, police said here.
Police had deferred arresting him because of a death in his family. Sarmokdam was due to retire soon, police added.
Seventy-four people died when a 7-story unauthorised building in Shil-Phata area near Mumbra in the district collapsed earlier this month.
The builders had allegedly bribed the corporation officials to turn a blind eye to the construction.