A bipartisan coalition of state attorneys general is expanding its investigation into Big Pharma's alleged role in the prescription painkiller and heroin addiction epidemic gripping the nation.

The group of 41 state AGs announced Tuesday that it is issuing subpoenas to several pharmaceutical drug manufacturers for information about how the companies market their opioids. The original investigation, launched in June, applied only to OxyContin and Dilaudid maker Purdue Pharma Inc. Now the investigation has grown to include Endo Pharmaceuticals Inc., maker of Opana and Percocet; Johnson & Johnson's Janssen Pharmaceuticals Inc., which makes Duragesic and Nucynta; Teva Pharmaceuticals USA Inc., maker of Actiq and Fentora; and Kadian manufacturer Allergan. The probe also extends to drug distributing giants AmerisourceBergen Corp., Cardinal Health and McKesson Corp.

An email seeking comment from the trade group representing the pharmaceutical industry, the Pharmaceutical Research and Manufacturers of America, declined to comment.