Nearly 780 million doses of oxycodone and hydrocodone were reportedly shipped to pharmacies and pain clinics in West Virginia in six years. (John Moore/Getty Images)

A congressional committee Monday opened an investigation into the Drug Enforcement Administration’s slowdown of enforcement efforts in the face of a national opioid epidemic and demanded to know why drug distributors had shipped hundreds of millions of painkillers to communities in West Virginia.

The House Energy and Commerce Committee sent letters to the DEA and the nation’s three largest drug distribution companies, giving them until June 8 to answer questions about their responsibilities to combat the rising epidemic, which has claimed nearly 180,000 lives during the past decade.

The letters follow reports in the Charleston (W.Va.) Gazette-Mail, The Washington Post and other news outlets about the flood of painkillers sent to West Virginia and the DEA’s role in holding drug distributors accountable.

“The opioid epidemic has devastated families across the entire country,” Reps. Greg Walden (R-Ore.), chairman of the panel, and Frank Pallone Jr. (D-N.J.) said in a joint statement. “These reports shine a light on a problem that many people have wondered about privately and publicly — how are opioids flooding into some of our communities and pharmacies?”

Last month, Sen. Claire McCaskill (Mo.), the ranking Democrat on the Senate Homeland Security and Governmental Affairs Committee, announced that she was launching an investigation into companies that manufacture opioids. In addition, nine U.S. senators have written letters to the DEA, requesting information about reports that it slowed its enforcement efforts against the pharmaceutical industry.

The House Energy and Commerce Committee said it would examine the nation’s three largest drug distributors, McKesson, Cardinal Health and Ameri-sourceBergen. Together, the companies distribute nearly 85 percent of the prescription drugs in the United States.

Late last year, the Gazette-Mail reported that drug distributors shipped nearly 780 million tablets of oxycodone and hydrocodone over six years to pharmacies and pain clinics in West Virginia. One pharmacy alone, in the town of Kermit, population 392, received nearly 9 million tablets of hydrocodone in two years.

West Virginia has the highest drug overdose death rate in the nation. In 2012, the state attorney general sued the distributors, securing a $36 million settlement from Cardinal Health and AmerisourceBergen. More recently, seven counties in the state sued the distributors, alleging that the companies were negligent in shipping so many drugs.

Representatives of McKesson issued a statement saying: “McKesson has strong programs and processes in place to stop the shipment of controlled substances to pharmacies with suspicious ordering patterns. Providing prescription medications to patients with serious medical needs without letting it get into the hands of bad actors is a healthcare industry-wide challenge.”

AmerisourceBergen said in a statement: “We understand the tragic magnitude of the opioid abuse problem in our country and we remain committed to working with stakeholders in health care and law enforcement to do what we can as a distributor to combat this problem.”

In a statement, Cardinal Health said: “We look forward to working together with the committee and responding to their letter. The people of Cardinal Health care deeply about the devastation opioid abuse has caused American families and communities and are committed to helping solve this complex national public health crisis.”

The panel also sent a letter to acting DEA Administrator Chuck Rosenberg, asking him to respond to reports in The Post that enforcement efforts against drug distributors slowed during a lobbying campaign by the industry. The Post cited internal DEA documents showing that the number of enforcement actions plummeted beginning in 2013.

“DEA continues to combat the opioid crisis on a daily basis through enforcement, outreach, and robust demand reduction efforts,” an agency spokesman said. “Specifically, DEA has increased the number of enforcement teams focused on criminal and civil investigations related to the opioid epidemic, and allocated additional resources to a successful drug take back program.”