BOSTON  On its face, it seemed reasonable enough: a bone marrow registry sending recruiters to malls, ballparks and other busy sites to enlist potential donors.

But the recruiters were actually flirtatious models in heels, short skirts and lab coats, law enforcement officials say, asking passers-by for DNA swabs without mentioning the price of the seemingly simple procedure. And the registry, Caitlin Raymond International, was paying up to $60,000 a week for the models while billing insurance companies up to $4,300 per test.

In New Hampshire, where prosecutors say thousands of people appeared to have provided swabs, the attorney general is investigating the registry’s marketing and billing practices. The registry is a nonprofit subsidiary of UMass Memorial Medical Center in Worcester, which said Thursday that it had stopped seeking donors in New Hampshire and using models altogether.

James T. Boffetti, the state’s senior assistant attorney general, said the registry had hired models based on their photographs and had given them “explicit instructions” to wear heels and short skirts. The registry paid the models to approach potential donors at dozens of malls and events throughout New England, Mr. Boffetti said.