The Drug Enforcement Administration said Friday that it had immediately suspended opioid sales by a wholesale distributor, accusing a Louisiana company of failing to report unusually large shipments of narcotics to independent drugstores “with questionable need for the drugs.”

It was the first time the agency had immediately cut off narcotic sales by a distributor in six years, Justice Department officials said.

The DEA said Morris & Dickson of Shreveport failed to “properly identify large suspicious orders for controlled substances sold to independent pharmacies,” in some cases sending out six times a drugstore’s normal order without notifying federal drug officials as required by law.

An investigation begun in October showed that the wholesaler sent the drugs to five of the top 10 purchasers of narcotics in Louisiana. “Not only were numerous independent retail pharmacies purchasing more oxycodone and hydrocodone than the largest chain pharmacies operating within the state, they were purchasing more narcotics than several of the largest chain pharmacies combined within the same Zip code,” the DEA alleged in a news release.

The 177-year-old company denied the charges. saying in a prepared statement that it could have shown the DEA it had done nothing wrong but was denied the chance. The statement said it has “voluntarily” rejected 142 pharmacies in recent years to avoid “improper distribution of opioids” — a number that amounted to an 8 percent reduction of Morris & Dickson’s customer base.

“Sadly, in this case, the DEA has gotten it wrong,” the company’s president, Paul M. Dickson, said in the statement. “We would’ve proved that to them had they given us the chance. But we’ll do that now in this administrative action and will help them improve their enforcement.”

Large, frequent or unusual drug orders can be signs that legitimate painkillers are being diverted to the black market by rogue drugstores. Federal law and DEA policy require that distributors — the middlemen in the drug distribution chain — notify the agency and hold back the drugs.

An immediate suspension order is the DEA’s most potent weapon, reserved for the most egregious cases.

In October, The Washington Post and “60 Minutes” reported in a joint investigation that Congress had passed a 2016 law that made it almost impossible for the DEA to employ that tool, by substantially raising the burden of proof on authorities.

The Post had earlier reported that for several years before the law’s enactment, some DEA attorneys had been slowing cases against wholesale distributors on their own, by requiring investigators to show ever-increasing amounts of evidence before they would approve immediate suspension orders or orders to show cause. The latter gives a company an opportunity to appear at a hearing before its drug supply can be cut off.

The Justice Department, some lawmakers and most state attorneys general have called for the 2016 law to be amended or repealed. In the meantime, Attorney General Jeff Sessions has vowed to include distributors in department efforts to curb the worst drug crisis in U.S. history.

In an interview with The Post on Tuesday, Sessions said the actions of some distributors have been “a colossal detriment to America, and [they] have profited enormously by it. And I’m not shedding any tears if you’re no longer making profits.”

Nearly 64,000 people died of drug overdoses in 2016 — the most ever in a single year — with opioids involved in about two-thirds of those. Deaths from fentanyl and heroin are increasing more rapidly than deaths from prescription drugs, but fatalities involving legal painkillers were up by 14 percent over 2015.

The death toll from all drugs is widely expected to rise again for 2017 when data becomes final, despite the number of prescriptions for legal opioids having fallen for several years.

Next week, leaders of the major drug distribution companies — including McKesson, AmerisourceBergen and Cardinal Health — are scheduled to testify before a House committee investigating years of sales that sent hundreds of millions of pills to pharmacies across West Virginia. In some cases, millions of pills went to tiny pharmacies in small towns that could not have supported that commerce through legal purchases.