What is the convergence criteria used in MATLAB lsqr function ?

I am using LSQR to solve Ax = b, where A is not consistent. I know that lsqr will give me the minimum residual solution. I am wondering within the lsqr routine, what is the convergence criteria (when does the algorithm terminate). Is it when where tol is some predefined small number, or is it something else. If it is something else, is there anyway I can change it ?

Thank you.