ISS current module configuration.
Yesterday morning the crew of Expedition 35 discovered they had a problem. Communicating with Mission COntrol in Houston, the crew used hand-held cameras to try to broadcast down what they described as "small white flakes" floating away from the station. NASA reports the leak, apparently of ammonia, is coming from the station's P6 Truss segment. This is an area where astronauts had previously made spacewalks to repair a leak in the coolant system. Now it appears there is still a problem.
Astronauts Sunni WIlliams and Aki Hoshide (Japan) on the November 2012 spacewalk to fix an ammonia leak.
Controllers on the ground were able to confirm there was a decrease in the ammonia supply in the coolant system. These coolant systems are important for the flow of electrical power from the giant solar power panels. For now, controllers and the crew are working to reroute the power channels away from the damaged system so that operations can continue as normal while a plan is considered for repairs.
While NASA reports there is no current danger to the life support systems, the engineers are giving a prediction that if the current leak continues, the affected coolant loop will have to be shut down in 48 hours.