(Forest Grove, OR)  --  Hazmat crews remain on the scene of an ammonia leak at a warehouse in Forest Grove.  The Forest Grove Fire Department says crews were still actively working to ventilate the 20-thousand-square-foot room where the leak occurred as of about 5 a.m. this morning.  The department says crews worked through the evening to stop the leak and ventilate the fumes.  Officials say there's still an odor of ammonia in the area but that the scene has been cleared and roadways have reopened.  Anyone experiencing difficulty breathing in the area is advised to call 911.