PROVIDENCE, R.I. (AP) — Rhode Island will get $15 million through a settlement with major oil and gas companies that allegedly polluted the state’s soil and groundwater with a gasoline additive, the attorney general announced Monday.

Rhode Island Attorney General Peter Neronha said the case, filed in 2016, alleged that Shell, Sunoco and Citgo, along with several other refiners, caused pollution with the gasoline additive methyl tertiary-butyl ether.

The companies agreed to pay $15 million to resolve the claims. The money will be used to remediate contaminated water supplies. Lawyers for the defendants either did not immediately respond to email messages seeking comment Monday or said they did not wish to comment at this point.

According to court documents, the defendants expressly deny any and all liability associated with the litigation, and believe they have good and valid defenses to all of the state’s claims. The defendants agreed to the settlement to resolve the lawsuit and avoid further costs, the documents state.

Neronha said the litigation is ongoing against several other major gas companies. MTBE has leaked from underground storage tanks, such as those typically found at gas stations, and contaminated groundwater and soil throughout the United States for decades, Neronha added. Rhode Island banned the use of the additive in 2007.

The state accused the companies of promoting and selling gasoline and other petroleum products containing MTBE, when they knew, or reasonably should have known, that the additive would be released into the environment and contaminate the state’s water supply, threatening public health and welfare.

Rhode Island has entered into separate settlements worth a total of $2.1 million with four other oil and gas companies.