India, May 11 -- A digital payment at a toll plaza near Kolkata has emerged as a key breakthrough in the murder investigation of Chandranath Rath, personal assistant to West Bengal chief minister Suvendu Adhikari.

Three people were detained from Bihar's Buxar district in connection with the case, police said, after investigators traced a UPI transaction allegedly made by the assailants while crossing Bally toll plaza in Howrah, as first reported by HT.

Buxar superintendent of police Subham Arya confirmed that a team from West Bengal had conducted raids in the district.

The silver car allegedly used in the attack crossed the toll point shortly before the shooting, with the occupants paying the toll via UPI payment.

"The UPI transaction...