A group of organizations and doctors is calling on the U.S. Senate to release records on the financial ties between opioid makers and nonprofit groups that advocated for the drugs’ use in treating pain. The records were obtained as part of an investigation, the Milwaukee Journal Sentinel reports.

The organization, called Fed Up!, is planning a rally in Washington, D.C. on October 3. The group sent a letter this week signed by 36 groups and individuals to Committee Chairman Orrin Hatch of Utah and ranking member Ron Wyden of Oregon. A spokesman for Wyden told the newspaper Wyden is committed to continuing the investigation and making the facts public.

U.S. Senators Chuck Grassley of Iowa and Max Baucus of Montana, who headed the committee when the investigation began, issued a joint statement saying there was growing evidence of extensive ties between companies that manufacture and market opioids and some nonprofit organizations. The list includes the American Pain Foundation, the American Pain Society, the American Academy of Pain Medicine and the Federation of State Medical Boards.

The committee also asked for records from Purdue Pharma, Johnson & Johnson and Endo Pharmaceuticals.

The Fed Up! coalition said the goal of ending the nation’s opioid epidemic will be difficult to achieve if opioid makers and the groups they fund “continue to promote aggressive and inappropriate prescribing.”

The group also hopes to expose the financial ties before new guidelines on the treatment of chronic pain are finalized by the Centers for Disease Control and Prevention. Andrew Kolodny, Executive Director of Physicians for Responsible Opioid Prescribing, said he expects pain groups will oppose the new guidelines.

“By making the findings of the investigation public and exposing the financial relationships between pain organizations and opioid makers, it will be harder for them to claim that it is the interests of pain patients they are lobbying for,” he said.