OxyContin-maker Purdue Pharma could be years away from paying billions of dollars to address the U.S. opioid crisis after a judge blew up a deal that gave provided legal immunity to the Sackler family that owned the company, people close to the negotiations said.

In a surprise ruling on Thursday, U.S. District Judge Colleen McMahon in Manhattan found that a bankruptcy judge overstepped his authority by approving the plan that gave the Sacklers immunity in return for $4.5 billion for those harmed by Purdue.

The deal had been hammered out over two years by U.S. states, local governments and others who had filed thousands of lawsuits accusing Purdue and the Sacklers of aggressively marketing OxyContin while downplaying its addiction and overdose risks.

The company and family members have denied the allegations.

Purdue said it will appeal McMahon's ruling, which it said would not impact its operations but will delay or even end the ability of states and others to receive billions of dollars.

Representatives for the Sackler family did not immediately respond to a request for comment.