The arrest of a man carrying 600 blank Air India boarding passes at Kolkata airport in March last year first alerted law enforcing agencies about the scam.
In November the same year, the CBI booked BJD MP Anil Kumar Sahani for allegedly drawing Rs. 9.5 lakh as travel reimbursement after submitting fake air tickets and boarding passes.
Besides the MP, Air India customer service agent Rubaina Akhtar and a Lajpat Nagar-based travel operator, Air Cruise Travels Private Ltd, were also named in the FIR.
Since then the CBI has noticed involvement of several more lawmakers. On Friday, the agency searched offices and premises of politicians and travel agents at 10 places in Delhi and Odisha.
TMC leader Derek O'Brien, however, accused the NDA government of using CBI for political vendetta.
"For years, the Congress government has used the CBI with a political motive. The BJP is following that sickening path," O'Brien told a news channel.
Renubala Pradhan said she didn't know anything about the scam and she would be traveling to Delhi to meet CBI officials, while confirming the agency sleuths had come to the residence of her cousin in Bhubaneswar.
(With agency inputs)