WASHINGTON — Executives at more than a dozen generic-drug companies had a form of shorthand to describe how they conducted business, insider lingo worked out over steak dinners, cocktail receptions, and rounds of golf.

The ‘‘sandbox,’’ according to investigators, was the market for generic prescription drugs, where everyone was expected to play nice.

‘‘Fair share’’ described dividing up the sales pie to ensure that each company reaped continued profits. ‘‘Trashing the market’’ was used when a competitor ignored these unwritten rules and sold drugs for less than agreed-upon prices.

The terminology reflected more than just clubbiness in a powerful industry, according to authorities and several lawsuits. Officials from multiple states say these practices were central to illegal price-fixing schemes of massive proportion.

The lawsuit and related cases picked up steam last month when a federal judge ruled that more than 1 million e-mails, cellphone texts, and other documents cited as evidence could be shared among all plaintiffs.

What started as an antitrust lawsuit brought by states over just two drugs in 2016 has exploded into an investigation of alleged price-fixing involving at least 16 companies and 300 drugs, said Joseph Nielsen, an assistant attorney general and antitrust investigator in Connecticut who has been a leading force in the probe. His comments to The Washington Post represent the first public disclosure of the expanded scale of the investigation.

The case is rattling an industry that is portrayed in Washington as the white knight of American health care.

‘‘This is most likely the largest cartel in the history of the United States,’’ Nielsen said. He cited the volume of drugs in the schemes, that they took place on American soil, and the ‘‘total number of companies involved, and individuals.’’

The victims were consumers and taxpayers, who foot the bills for overcharges on antibiotics, blood pressure medications, arthritis treatments, anxiety pills, and more, authorities say. The costs hit hospitals, pharmacists, and health insurers. They hit consumers who lack prescription drug coverage and even those with insurance, because many plans have high deductibles and gaps on prescription drug benefits.

In just one instance of extraordinary cost spikes, the price of a decades-old drug to ease asthma symptoms, albuterol, sold by generic manufacturers Mylan and Sun, jumped more than 3,400 percent, from 13 cents a tablet to more than $4.70. The example is documented in a lawsuit brought by grocery chains including Kroger.

‘‘Everyone is paying the price,’’ Nielsen said. He offered a single word to explain the behavior: ‘‘greed.’’

While precise estimates of alleged overcharges have not been released, generic-industry sales were about $104 billion in 2017. Excessive billings of even a small fraction of annual sales over several years would equal billions in added costs to consumers, investigators say.

Manufacturers reject the accusations. They contend officials lack evidence of a conspiracy and have failed to prove anti-competitive behavior.

Among the 16 companies accused are some of the biggest names in generic manufacturing: Mylan, Teva, and Dr. Reddy’s. Mylan denied wrongdoing. Sun, Teva, and Dr. Reddy’s did not respond to requests for comment. In a court filing, Teva said allegations of a price-fixing conspiracy ‘‘are entirely conclusory and devoid of any facts.’’

But investigators say voluminous documentation they have collected, much of it under seal and not available to the public, shows the industry to be riddled with price-fixing schemes. The plaintiffs now include 47 states. The investigators expect to unveil new details and add more defendants in coming months, which will put more pressure on executives to consider settlements.

Two former executives of one company, Heritage Pharmaceuticals, have pleaded guilty to federal criminal charges and are cooperating in a parallel criminal case. A Justice Department spokesman declined to comment.

The alleged collusion transformed a cutthroat, highly competitive business into one in which coordinated price spikes on identical generic drugs became almost routine.

‘‘It’s particularly ironic since the whole idea of generic drugs was we would get a lower price,’’ said Henry Waxman, the Democratic former California congressman who co-wrote the 1984 law establishing the Food and Drug Administration’s rules for generics. ‘‘If generic versions are higher than need be through rigged systems, that undercuts the whole idea.’’

Generics account for 90 percent of the prescriptions written in the United States but 23 percent of costs, according to the industry group, the Association for Accessible Medicines.