Releasing feature class after using MakeFeatureLayer

I am using ArcObjects to call GP tools.
Most tools does not leave any locks and the data can be deleted after the tool is done.
The MakeFeatureLayer is different. It gets a feature class and return a string so there is no COM object I can release.
I did release the feature class and the workspace but the feature class is still locked.
I tried to cast the IGeoProcessorResult.getOutput into ILayer so I can release it but it fail.
I know I can get the feature class using DecodeFeatureLayer but it does not help me to clean up.
I am using MakeFeatureLayer, do something with that layer and then would like to delete the feature class.

Please help