My uncle took out a loan using our family property as collateral without telling us?

I just found out that my uncle, who manages our family property in Hyderabad, took a loan by mortgaging it. My father had trusted him with the paperwork, but none of us were informed about this loan. We are shocked because the bank has now threatened to seize the property as he hasn't been paying the EMIs. What legal actions can we take to stop this and protect our property?