2010 Questions for all other cars Smell of mud or wet soil f

Dear Sirs,

My 20 days old Suzuki Estilo's (1000 CC) AC is giving the smell of mud or wet soil for two minutes when AC is swiched on after a gap of 3-4 hours. There is no smell when heater is on. The problem is more evident when I drove the car through wet roads with water on the road.

Please let me know what could be the reason for this and how to rectify it.

Thanks.
Sincerely.
Antony Renji
India