Some of the world’s biggest music publishers have filed a major lawsuit against artificial intelligence company Anthropic, accusing the firm of “one of the largest and most blatant ongoing thefts of intellectual property in history.”

The lawsuit, filed late Friday, marks the beginning of what could become a yearslong legal battle over the use of music in artificial intelligence systems and the future of copyright protection in the rapidly developing technology era, according to Axios on Saturday.

Companies affiliated with Sony Music and Warner Music brought the case before a federal court in Northern California. Anthropic CEO Dario Amodei and co-founder Benjamin Mann were also named as defendants.

In their 48-page complaint, the plaintiffs accuse Anthropic and its founders of systematically obtaining copyrighted material without permission in order to develop and operate the company’s artificial intelligence models.

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“Defendants Anthropic and its founders Dario Amodei and Benjamin Mann have conducted a brazen campaign of illegally torrenting, scraping, and downloading copyrighted works on a massive scale in order to develop, operate, and reap enormous profits from Anthropic’s ‘Claude’ series of artificial intelligence (‘AI’) models,” the plaintiffs said in the complaint.

The music publishers alleged that Anthropic illegally copied thousands of copyrighted musical works. They are seeking hundreds of thousands of dollars in damages for each work they claim was infringed.

The case is not the first legal challenge facing Anthropic over allegations that copyrighted material was used to train its AI models.