LUCKNOW, Aug. 7 -- The Uttar Pradesh Vigilance Establishment has widened its investigation into the Rs.7.5 lakh Lucknow Development Authority (LDA) bribery case after concluding the custodial interrogation of alleged middleman Shravan Kumar, recovering key digital evidence, and obtaining a list of the top 50 "professional complainants" who repeatedly flagged alleged illegal constructions through the Integrated Grievance Redressal System (IGRS) and other platforms, officials said.

Investigators are probing whether a nexus existed between habitual complainants, private middlemen and officials in the LDA's enforcement wing to allegedly extort money from property owners by threatening demolition or other enforcement action.

Shravan Kumar, a...