Answer
(Fatwa: 659/659=M/1430)
If you are sure or most probably your father paid the bank loan with bribe money or the property was purchased purely by bribe money, in this case it is necessary to return the amount to their original owners (those who have given in bribe) if they are known. But, if the owners are not known, the amount should be given in charity. If the income of your father was mixed and you are not sure that he purchased the property purely with bribe money, in this case the heirs can utilize his property.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband