The interior of the car smells heavily of gas

Your Toyota's fuel system consists of multiple components that make up the storage and delivery system. Some of these components such as the fuel pump are accessed from within the vehicle cabin, in this case under the rear seat. The fuel delivery lines travel under the vehicle and the fuel filter and charcoal canister are located on the driver side fire wall. Keep in mind the fuel system is under high pressure and a leak can be very dangerous and if the system does not show signs of a leak, gasoline vapors are equally concerning. I strongly recommend you have the vehicle inspected by a service center as soon as possible.

You need to have a shop check this ASAP and you can find one herehttp://repairpal.com/toyota-repair-in-annapolis-maryland Probably leaking at or near the fuel filler