Sorry not much detail, vague memories from youth.
Think it may have aired in the 1970s, and was about an archeology dig somewhere in New Zealand on Maori sacred land that unleashes a disease of some sort. In the final episode someone discovers something startling just before a major cave in. That's about all I can remember of it.
Am trying to a) get a title, and b) hopefully source a DVD release for an episode guide.