Finding IRAs?

My dad passed away 1/1/06.

My grandmother has several IRAs listed with my dad's name and her name on the account. These IRAs could be at different banks. My grandmother is getting up there in years and doesn't remember what banks or how many IRAs she has. My uncle (dad's brother) takes care of my grandmother's checking account and he won't say anything other than "there's nothing in the account". IMO: If there's nothing in the account, then why isn't it closed? hhmmm??!!

Is there anyway my mom, who is the executor of my father's estate, get the money from these IRA accounts without my grandmother's signature?

Also, is there any way a search could be done to find out what IRAs are listed under my dad's name?