Flexible Job Shop with Preemption

I’m trying to solve a flexible job shop problem variant that has precedence constraints on jobs along with a few other issues. We have a MIP formulation and also a simulated annealing algorithm to solve at the moment. But now we would like to allow preemption of jobs (leaving a job and coming back to finish it later, possibly times).
Do you have any thoughts on how to model the problem to allow for preemption?