LUCKNOW, Dec. 5 -- An alleged "critical linkman" in the interstate and international codeine-based cough syrup trafficking chain has remained untraceable even as the Uttar Pradesh Special Task Force (STF) has intensified its crackdown on the syndicate.

The key figure, Vikas Singh 'Narve', has been repeatedly mentioned during interrogation by every major accused, including Jaunpur resident Amit Kumar Singh alias Amit 'Tata', dismissed constable Alok Pratap Singh, resident of Chandauli, and Bhola Prasad Jaiswal, the father of the fugitive kingpin Shubham Jaiswal, according to people privy to the investigation.

Officials describe him as the "organisational glue" holding multiple nodes of the nexus together. The STF maintains that efforts a...