Apparently, two young opossums had made a nice nest in the engine compartment while the car was not in use.
When we arrived, the local animal control was just leaving (empty handed).
Workers at the shop were extremely helpful in assisting us in locating the marsupials. We had the car lifted and the shields removed. One ran out during the process, and was captured. The other was found hiding on top of the exhaust pipes.
We had help from mechanics who used pressurized air to encourage the animal in our direction.
Both animals were released that evening in their home territory.