According to an aspect, there is provided a local diagnosis system comprising means for performing the following. The local diagnosis system detects one or more anomaly events associated with a communications network. Each anomaly event defines an anomaly pattern describing a data point in a performance indicator space. Then, the local diagnosis system updates one or more local cluster models to incorporate the one or more anomaly patterns within complexity constraints. Each of the one or more local cluster models corresponds to a different diagnosis label defining a diagnosis. In response to failing according to one or more pre-defined criteria to incorporate, in the updating, the one or more anomaly patterns to the one or more local cluster models, the local diagnosis system forwards at least the one or more local cluster models and one or more associated diagnosis labels to a central diagnosis system for further diagnosis.