What was found
(CAN) FUSELAGE DOOR WARNING LIGHT APPEARED ON ROTATION. DOORS PAGE ON MFD DISPLAYED A FWD CARGO DOOR UNSAFE CONDITION. QRH RAN WHICH EXTINGUISHED THE LIGHT, HOWEVER THE F/A REPORTED HEARING A LOUD WHISTLING NOISE AND THE DECISION WAS MADE TO TURN BACK TO ORIGINATIING AIRPORT FOR INVESTIGATION. NO EMERGENCY WAS DECLARED AND NO INJURIES REPORTED. ON INSPECTION BY CREW, SOME ICE WAS CLEANED OFF BOTH THE SENSOR AND SEAL OF THE FWD CARGO DOOR. RTS. NO FURTHER DEFECTS NOTED.