The Sanctity of the Dead Muslim is the Same as That of the Living
Question :
If a man wanted to build a house, extend one, or erect any other building in a stretch of land on his farm, but while building, he found one, two, three, four or more graves what should he do?
Answer:
Originally, they were buried in land which was unculti- vated, of which they became possessors when they were buried therein, so it is not permissible to interfere with them, neither by excavating them, nor by making a path or road, nor abusing them. They must be surrounded by a wall and it must not be allowed for anyone to mistreat or abuse them, and they must be protected for the sake of the dignity of their inhabitants. This is because the sanctity of the deceased Muslim is the same as his sanctity while he was alive. And may peace be upon our Prophet, Muhammad and upon his family and Companions.
Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 5 Pages 41-42