"Having consulted with our French colleagues, they have confirmed that through their own research, 70 per cent of migrants they process in the area of Calais leave the vicinity within a four-month period," Alan Pughsley said as quoted by the Daily Mail newspaper.
French police cannot determine whether the migrants move within France or manage to enter the United Kingdom, Pughsley added.
UK police can confirm that over 400 migrants were caught in Kent County alone over the past five weeks, while the real figures might be "a lot higher," he stressed.
The newspaper projected that some 3,500 of the estimated 5,000 migrants currently in Calais would pass through the Channel Tunnel and enter Britain in the near future.
The crisis in Calais has come to the fore in recent weeks with undocumented migrants undertaking thousands of attempts to enter the United Kingdom through the Channel Tunnel, resulting in several migrant deaths and severe traffic disruptions.
