The plot thickens: Mazda engineers are hard at work trying to develop a rival to the Chevrolet Volt, Autocar is reporting. That means the company is working on a car that's not a hybrid, but instead uses a gas engine to charge a battery pack that powers the car via an electric motor.

The report said that trials are currently underway in Japan, according to unnamed "senior sources" at the company, with a prototype that uses a (get this) rotary engine to charge the battery pack. The sources said that Mazda has already fitted a test drivetrain in a Mazda 5 MPV bodyshell, but is still working out how to reduce the costs of the batteries before putting the car into production.