Should I pay for the repair - kitchen ceiling water leak?

I am on a 2nd floor condo, my neighbor downstairs complained that his kitchen light fixture fell on the floor due to sagging ceiling from water damage. However, I could not find any water leak or overflow in my unit. Should I pay for the repair? Note: It has been weeks, all dry and good. No one want to pay for the costly investigation (opening the walls) to find out the exact cause. The condo is in Dallas, Texas.