The billionaire Sackler family “funnelled” at least $1bn (£800m) to different banks, including accounts in Switzerland, officials said.
The Sacklers own Purdue Pharma, which is accused of fuelling the US opioid crisis through drugs like OxyContin.
Purdue is currently facing legal action brought by more than 2,000 plaintiffs, including almost two dozen US states.
Forbes estimates the Sacklers are worth $13bn, but many states claim the family has more money hidden abroad.
New York State Attorney General Letitia James said that she has requested records from 33 financial institutions. However, the $1bn in wire transfers were revealed in records from just one institution.
“Records from one financial institution alone have shown approximately $1 billion in wire transfers between the Sacklers, entities they control and different financial institutions, including those that have funnelled funds into Swiss bank accounts,” Ms James said, confirming claims first reported in the New York Times.
She did not name the financial institutions involved.
In response, a spokesperson for Mortimer DA Sackler, a former board member for the company, said in a statement to US media that there was “nothing newsworthy about these decade-old transfers, which were perfectly legal and appropriate in every respect”.
“This is a cynical attempt by a hostile AG’s office to generate defamatory headlines to try to torpedo a mutually beneficial settlement that is supported by so many other states and would result in billions of dollars going to communities and individuals across the country that need help,” the spokesperson added.
What is the latest with the case?
It was reported on Thursday that Purdue Pharma reached a tentative multi-billion dollar agreement to settle the lawsuits against it.
According to the draft agreement, the Sacklers are expected to give up control of Purdue Pharma and personally contribute $3bn to the settlement.
The company would then file for bankruptcy, dissolve and reform, and would be removed from next month’s legal proceedings.
However a number of states, including New York, Massachusetts, and Connecticut, where the company is headquartered, said they were not party to the deal and would continue their fight against the company.