SHAFAQNA – The Grand Ayatollah Fayyaz answered a question about lands with unknown landlords.
Question: What is the ruling on using lands without landlords or unknown landlords?
The Grand Ayatollah Fayyaz: Anyone who cultivates the wasteland can become its landlord. But regarding lands with unknown landlords; firstly, must look for the landlord or inheritors of the land, if they are not found, only by the permission of the religious authority, or his lawyer/counsel, it can be used.
Source: PERSIAN SHAFAQNA