Multiple Clock-In Clock-Out entries at a particular time

Dear   Friends,

For some employees, in IT2011 it shows multiple Clock-in(P10) and Clock-out (P20) entries at a particular time.

Please let me know the root cause for it and steps to resolve it.  It's not possible to delete manually so many records for a number of employees.

Attaching the screenshot

Regards,

Nayak