Verb (past participle): This is when "buried" describes an action that has already happened, often used in the context of being placed in the ground:
* *The treasure was buried deep in the forest.*
* *He buried his face in his hands.*
Adjective: This is when "buried" describes a state of being, meaning something is covered or hidden:
* *The city was under buried in snow.*
* *She had a buried secret.*
The context of the sentence will determine which part of speech is being used.