Hyundai is reportedly working on a compact hybrid car, and several development mules of the potential Toyota Prius rival were caught testing in public.

AutoGuide has a gallery full of photos, and reports that while the mules used current five-door Elantra GT bodyshells, not to expect a hybridized Elantra, but rather a standalone model.

The rough appearance of the development mule shouldn’t be an indication of the final result, of course, but apparently one example was modified enough in the rear to suggest two models are forthcoming. One variant could tackle the regular Prius, the other the larger family-oriented Prius V. AG says that the battery packs were located under the rear seats, with obvious high-voltage cables running both inside and underneath.

No word on important details like engine size, electric motor output or batteries used, but Hyundai did show off a concept in 2010 that had a 1.6-liter four-cylinder and 100-kw electric motor at its heart.

Hyundai’s experience with hybrids has been mixed, with the Sonata hybrid appealing to drivers who don’t like CVT transmissions, but lags behind its competitors in real-world fuel consumption. And, the second-generation hybrid has been delayed until 2016, leaving the current version in place until then.