remove some lines of .txt files in bash
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In my current directory of have couple of .txt files I want to write an script to search for a  
string in those .txt files and delete that line which contains that string in all .txt files.
Like deleting all lines which has word "start" in all .txt files in my current directory.
I have started my code like this but I don't know how to continue!

    #!bin\bash
    files=`find . -maxdepth 1 -name \*.txt`

How should I use "while" to go through of each file? 
