The officers were tipped off to the possibility of a scam because nearly 300 such tickets were being sold in Mumbai everyday, said sources in the Vigilance Department. A compilation of tickets issued for three days from July 14 showed that that even after the first batch of the accused were arrested on July 9, the sale of tickets continued unabated for nearly a week.

On July 14, nearly 320 tickets were issued on the pass in Mumbai. Mumbai CST topped the list with 195 tickets while Kalyan came second with 64. The next day, over 325 tickets were sold, CST selling 225 and Kalyan 40.

On July 16, a comparatively low sales figure of 270 was recorded. On this day, sales at CST recorded a sharp fall to 172, while sales at Kalyan remained unaffected at 50.Thereafter, there has been a steady decline in the sales.

Vigilance officers believe that the high sales figures in the first few days indicate that the public had not realised that the racket had been exposed. ``After the matter appeared in the press, these pass holders are shy of approaching us for tickets,'' said an official.

These privilege passes are given to officers in the grade of the Heads of Departments (HODs), said a CR spokesperson. But, if the huge sales seem to indicate a exodus of HODs, then it is cause for concern as well. ``We will have to find out how so many senior railwaymen got leave to go out during the same period,'' said an officer.

Though no one has been caught either by the Vigilance Department or the Railway Police in the past few days, senior officers also admit that sale of tickets through these passes might not have stopped. This is likely to be the focus of the investigation now.

The scam, which was exposed when the servant of a Congress Seva Dal leader Chandrakant Daymawas caught trying to book a ticket using a fake VIP pass, is already under investigation by the Government Railway Police.