UMass Memorial Health Care is being investigated by authorities in New Hampshire over "suspect marketing and billing practices", Michael Delaney, the state's attorney general said.
Its bone marrow registry is accused of paying an agency up to $50,000 (£32,000) a week for models to visit shopping centres, flirt with passing male customers and coax them into having cheek swabs taken.
The models, who were in their 20s, allegedly told the men the tests would barely cost anything, before billing them an average of $4,300 (£2,770) each via their health insurance – about 40 times more than the typical cost.
For 18 months, they were instructed how to dress and how to behave in an attempt to entice men into having swabs taken, officials said.
It is claimed they happily took samples from people who weren't eligible because of their age, medical profile or because they were already on a national registry.
"Picture this," Mr Delaney said. "The modelling agency sends photographs to the marketing director at UMass for personal selection of models to go recruit donors to save people's lives. It's unbelievable."
The company said it had used models "to help acquaint the public on how they can contribute to this lifesaving effort", but had since stopped sending them to kiosks in shopping centres.
In a statement, the hospital group said: "Every potential donor is provided with a donor consent form that explains that his or her insurance company may be billed". It added that the company "has reviewed its billing practices for this test and confirmed to its best knowledge that it is appropriately paid".
A spokesman declined to comment on the claim that ineligible people were signed up as donors.