CONCORD, N.H. — The New Hampshire Attorney General’s office is targeting the maker of Oxycontin, a top selling prescription painkiller, with an investigation into whether it downplays the risks of addiction when marketing pain pills to doctors and other prescribers.

But Connecticut-based Purdue Pharma for now is refusing to respond to a subpoena seeking documents that show how it sells and markets drugs in New Hampshire. It also is fighting New Hampshire’s decision to hire a law firm to aid in the investigation.

The company won a court argument that delayed the turnover of documents for months, but the attorney general’s office made a new pitch for compliance last week.

State lawyers say a clear picture of how painkillers are marketed and sold is critical to curbing New Hampshire’s growing drug addiction crisis, which caused more than 430 overdose deaths in 2015.

“Given Purdue’s ongoing marketing and the rising toll — of death, overdose, addiction, and abuse in New Hampshire — there is every reason to move forward promptly,” the attorney general’s office wrote in court documents filed Friday seeking to force Purdue to comply with the subpoena.

Purdue is the largest brand-name manufacturer of drugs prescribed in New Hampshire, Attorney General Joe Foster said. He said Purdue drugs account for 20 to 30 percent of dollars spent on brand-name prescription pills. Purdue, meanwhile, points to data that show OxyContin made up 6 percent of all opioids prescribed in New Hampshire in 2014. And the company is no stranger to lawsuits: It pleaded guilty and paid a $630 million settlement in 2007 for federal charges that it misled doctors and patients about the risks of OxyContin. The OxyContin the company now produces uses a new formula that the company claims is less addictive.

The new court filings allege Purdue is continuing to “engage in the type of deceptive marketing” that resulted in the 2007 settlement.

“Purdue sales representatives continue to make sales visits to New Hampshire doctors during which they misleadingly portray or omit the risk of addiction,” the court filing says, adding that Purdue representatives made 217 sales visits in New Hampshire in 2014. The filings also cite an investigation by the Los Angeles Times into Purdue’s marketing practices.

Purdue successfully delayed turning over documents, first requested in August, by challenging the attorney general’s hiring of the law firm Cohen Milstein to aid in the investigation. Foster initially contracted with the firm on a contingency fee basis, meaning the amount of the firm’s payout would depend on the results of litigation. He did not seek legislative or executive council approval for the contract.

New Hampshire hasn’t filed any charges against Purdue, but the company said Cohen Milstein has a “special financial interest” in the results of the investigation. Cohen Milstein is representing Chicago and a county in California in lawsuits against drug companies.

A judge ruled in March that the contract needed legislative and council approval. Both recently approved Cohen Milstein’s hiring with a flat $100,000 attached, prompting the attorney general’s fresh demand for Purdue to turn over documents. But Purdue still refuses, citing pending appeals in court.

A spokesman for the company says it will turn over the documents if the attorney general’s office stops working with Cohen Milstein.

“Purdue has repeatedly made clear that it is willing to work with the attorney general’s office on its investigation,” spokesman Robert Josephson said in a statement. “However, we’ve raised a very serious issue about whether it is proper for government enforcement powers to be privatized to outside counsel with a special financial interest.”

Foster said without outside help, his office does not have enough resources to investigate Purdue. The state’s consumer protection bureau has four lawyers, and Purdue has hired multiple private firms for the case.

“What they want to do is take one arm behind our back,” Foster said.