What should be done by those who built a mosque and then learned that there is a grave beneath it?

Question:
In the village, they built a mosque and spent a great deal of money on it. Then, after they finished building the mosque, it became clear to them that they had built it on a grave. They say: If we demolish the mosque after spending so much money on it, would that not be wasteful?

Answer:
No, the grave should be dug up. Did they not intend to build on it?
The student: Yes, exactly.
The Shaykh: The grave should be dug up, just as the Prophet (peace and blessings be upon him) dug up the graves.
Q: Even if the mosque was built on the grave?
The Shaykh: Even if it was, the grave should be dug up and moved away. They did not intend to build on the graves.