بسم الله الرحمن الرحيم
The bank interest received by bank may not be used for construction of personal toilet or that of a mosque or madrasa. Such an amount should be distributed in the poor, needy and debt-ridden ones without an intention of reward.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.