MINNEAPOLIS (AP) — Federal authorities in Minnesota have charged 21 people with conspiracy to commit health care fraud in what they describe as separate scams by six chiropractors that defrauded auto insurance companies out of more than $20 million.

And U.S. Attorney Andrew Luger told reporters Wednesday that more charges against additional chiropractors are likely.

The chiropractors allegedly billed auto insurance companies for treatments that people who had been in accidents didn't need, and in some cases never received. The chiropractors allegedly paid illegal kickbacks to "runners" to bring in accident victims, and some of the "runners" in turn paid kickbacks to patients to ensure they kept coming back for unnecessary appointments.

FBI Special Agent in Charge Richard Thornton says Minnesota auto owners pay higher insurance rates because of this kind of fraud.