(Reuters) - Montana has sued OxyContin maker Purdue Pharma LP, withdrawing from a multistate investigation by attorneys general into opioid manufacturers’ marketing practices and joining a growing list of states that have broken off to pursue individual lawsuits.

FILE PHOTO: A pharmacist holds prescription painkiller OxyContin, 40mg pills, made by Purdue Pharma L.D. at a local pharmacy, in Provo, Utah, U.S. on April 25, 2017. REUTERS/George Frey/File Photo

Montana Attorney General Tim Fox announced a lawsuit on Monday accusing Purdue of misrepresenting the likelihood that long-term use of painkiller would lead to addiction and of falsely claiming it was safe for treating chronic pain.

“Pharmaceutical companies that knowingly and deceptively harm consumers must be held accountable,” Fox said in a statement.

Purdue in a statement denied the allegations. It has argued its medications are U.S. Food and Drug Administration-approved for long-term use and carry warning labels about their addiction risks.

“We are deeply troubled by the opioid crisis and we are dedicated to being part of the solution,” Purdue said.

Opioids were involved in over 33,000 deaths in 2015, according to the U.S. Centers for Disease Control and Prevention. President Donald Trump in October declared the problem a national public health emergency.

State attorneys general have been conducting a multistate investigation into whether companies that manufacture and distribute prescription opioids engaged in unlawful practices.

Increasingly, some attorneys general have withdrawn from the probe to pursue lawsuits against drugmakers including Purdue, claiming they engaged in deceptive marketing that underplayed opioids’ risks.

Purdue faces lawsuits by at least 11 states besides Montana. It also faces lawsuits by cities and counties nationally and a federal probe by the U.S. Attorney’s Office in Connecticut.

Plaintiffs lawyers involved in the cases have compared them to the litigation by states against the tobacco industry that led to 1998’s $246 billion settlement.

Stamford, Connecticut-based Purdue and three executives pleaded guilty in 2007 to federal charges related to the misbranding of OxyContin and agreed to pay a total of $634.5 million to resolve a U.S. Justice Department probe.

That year, Purdue also reached a $19.5 million settlement with 26 states and the District of Columbia. It agreed in 2015 to pay $24 million to resolve a lawsuit by Kentucky.

The current multistate probe was announced publicly after Ohio Attorney General Mike DeWine withdrew from it and in May sued Purdue, Endo International Plc, Johnson & Johnson, Teva Pharmaceutical Industries Ltd and Allergan Plc.

Purdue in a letter last week urged DeWine to avoid litigation by rejoining the multistate probe, where officials have said they are exploring if early settlement opportunities exist.