Buzzing Sound Left Rear of Prius 2018 Prime Advanced

I have been driving a Prius since 2005 and know that occasionally a motor or pump will run after you turn off the car however on two occasions now I have went into the garage hours after my new Prius Prime Advanced with 700 miles has been turned off and I hear what sounds like a motor or pump running and it seems to be coming from the left rear of the car. Once it ran for at least five minutes so I started the car, waited for the Ready light and turned it off and the motor had stopped, Today I went into the garage about five hours after the car had been turned off and I heard the sound coming from the left rear. It stopped on its own after about 5 min but I don't know how long it was running before I heard it. Is this normal?? I did not take it to the dealer as it will only do it occasionally, Is there a fuel pump in that area?