Italy's competition watchdog said Friday it was investigating four electric vehicle makers, including Tesla and Stellantis, for alleged unfair commercial practices.

The four separate probes are targeted at BYD Industria Italia, Stellantis Europe, Tesla Italy and Volkswagen Group Italia, all Italian or European subsidiaries of the multinational automakers.

The investigations relate to information provided to consumers on driving range, battery degradation and limitations on battery warranties, all "potentially in breach" of Italy's consumer protection laws," wrote the Italian Competition Authority in a statement. 

"The companies’ websites appear to have displayed generic – and at times contradictory – information regarding the driving range of their marketed electric vehicles, without clarifying which factors impact the advertised maximum range and the extent to which they affect the actual range," it said.

The websites also fail to give "clear and complete information" on how the capacity of their electric vehicle batteries can degrade from normal vehicle use, and on the limitations of the warranties offered. 

The watchdog said it had carried out an inspection at all four companies Thursday, together with Italy's financial police. 

Stellantis said it had provided "adequate, accurate and comprehensive answers" to authorities and was cooperating with the probe.

Tesla, Volkswagen and BYD did not immediately respond to requests for comment. 

The lifespan of electric vehicle batteries are dependent on multiple factors. Degradation, which reduces energy capacity, can occur due to extreme cold weather and inconsistent charging.