The US state of Pennsylvania is suing 50 oil and petrochemical producers over groundwater pollution caused by leaks and spills of gasoline containing the chemical additive MTBE.

Defendants include MTBE manufacturers, gasoline refiners, marketers and distributors that together controlled virtually the entire market in Pennsylvania, according to the lawsuit.

Pennsylvania said it wants to recover the more than $738 million it has spent to investigate and clean up about 3,400 gasoline spills or leaks since 1994, a substantial portion of which have involved MTBE.

The lawsuit charges that the companies' conduct was "wanton, malicious, oppressive and fraudulent" and that they "fraudulently, deceptively and unfairly" marketed MTBE as safe for the environment.

MTBE, which as Pennsylvania notes "has been identified by the US Environmental Protection Agency as a "potential human carcinogen at high doses," has been detected in groundwater throughout the state.

The lawsuit follows a US Supreme Court decision in April not to overturn a $105 million verdict against ExxonMobil for contaminating New York City's groundwater.

Vermont filed a similar MTBE lawsuit earlier this month and New Hampshire last year won a $236 million verdict against Exxon Mobil.