The body isn’t empty when a person dies. Leftover food, for example, often remains in the digestive tract. The muscle relaxation that occurs as soon as death takes place may therefore cause the body to release feces or urine following death (via Bustle). Similarly, just as undigested food may be found in the stomach or bowels, unreleased air may still be in the lungs after death. As the body is moved, the expulsion of that air can produce sound. This is often the case if cardiopulmonary resuscitation (CPR) has been performed on the body.
“When a doctor or someone tries to resuscitate a person, extra air gets pumped into the patient’s lungs and stomach,” health and wellness expert Caleb Backe told Bustle. “After you’ve died, the air can still escape if someone applies pressure to the body while moving it. It could sound like moans, groans, and even squeaks.”