Common basement moisture paths
Look for plumbing leaks, foundation moisture, condensation on cool surfaces, wet carpet or padding, damp stored items and past water events. The cause matters because surface cleaning without correcting moisture can allow mold to return.
Materials matter
Hard, nonporous surfaces may be cleanable depending on the situation, while porous materials can be more difficult to clean completely once mold has penetrated them.
A practical next step
If the area is widespread, repeatedly returns, is tied to extensive water damage, or extends behind finished walls, professional evaluation can help define the scope.