What was found
ON CLIMB OUT @ 4000' FA'S CALLED WITH AN EXTREMELY LOUD SQUEAL FROM R1 DOOR. LEVELED OFF AT 9000', THEN THE FA CALLED SAYING THEY SAW A HAZE IN THE CABIN. GROUNDED - YES. DIVERSION TIME 12 MINUTES - FOUND WATER BOTTLE CAP ON R-1 THRESHOLD - SUSPECT CAUSE OF NOISE. REF AMM 52-41-00-200-802, PERFORMED GVI OF DOOR R-1 PRESSURE SEAL, NO DEFECTS NOTED, PRESSURIZED AIRCRAFT TO 4 PSI, NO SQUEAL NOTED. RAN BOTH PACKS FOR MORE THAN 15 MINUTES, NO EVIDENCE OF A HAZE NOTED INSIDE THE CABIN. REF AMM 05-51-91-790-801.