My sister and I used to watch a movie in the 80s when we were about 10. It was about a family who moved into a large mansion. And, back in the olden days a family had lived there that was robbed and a girl escaped through the fireplace into a tunnel. The current family goes through a similar situation and get in the tunnel and find the girls body solving the mystery of what happened to her.

Any help would be great!

Sounds like Mystery Mansion (1983) (http://www.imdb.com/title/tt0091587/)