Both Nassiri and Noorda were reached by telephone Monday but had no comment.

Shelley Beeler, a spokeswoman for Allstate's southwest region, which includes Nevada, said the estimate of fraudulent payments is unknown but is believed to be in excess of $75,000.

The case and others like it are brought by the company when evidence of fraud is uncovered, she said. A complaint filed in Texas earlier this month is seeking $10 million.

Beeler said fraud can add hundreds of dollars each year to the cost of a consumer's auto insurance policy. The company has a special investigations unit that continually looks for evidence of fraudulent activity, she said.

In the complaint, Allstate alleges that Nassiri, Noorda and their related businesses fraudulently submitted bills for treatment that was not performed, was medically unnecessary or was inadequately performed, and that the medical providers submitted medical reports that falsely claimed injuries that had not actually been sustained.

It says the incidents occurred between 2001 and 2007 and involved, "a pattern of racketeering activity," as defined in federal law.

The lawsuit alleges Nassiri and Noorda typically sent bills to the attorneys representing the injured individuals, and that they were ultimately paid directly from the proceeds of any judgment or settlement.

"The records, facts and evidence reveal very severe, and strikingly similar, clinical inconsistencies in the conduct of defendants, all of which do not support medical necessity or reasonableness of the chiropractic treatment incurred at the various facilities, the referrals and elevated billings," the lawsuit says.

The complaint says that Noorda consulted on many of Nassiri's claimants and often saw patients at Nassiri's Advanced Accident office.

The complaint also says that Allstate believes other physicians have conspired with Nassiri and Noorda and that others might be named in the complaint later.

The complaint says that a chief referral source for Nassiri and Noorda was Las Vegas attorney Adam Kutner. If a claimant did not have an attorney, Nassiri and Noorda would refer them to a local attorney, "like Adam Kutner," the complaint says.

Attempts to reach Kutner Monday at his Las Vegas office were unsuccessful.

The complaint says that Nassiri's reports and clinical records for various claimants "were filled with verbatim descriptions and identical statements, regardless of the circumstances of the accident, or the age and physical condition of the claimant."

In one case, Nassiri saw a claimant on the same day as the auto accident and said the claimant was having trouble sleeping. But the examination occurred before the claimant had the opportunity to sleep, according to the complaint.

"The multitude of improbable signs that were reported by defendants for each claimant (especially considering that most were not supported within reasonable medical certainty) was more consistent with defendants creating and/or exaggerating a claim rather than for bona fide assessment of a claimant's true clinical condition," the complaint says.

The Chiropractic Physicians' Board of Nevada lists no disciplinary actions against Nassiri. The state Board of Medical Examiners lists Noorda as a general practice medical doctor with no disciplinary actions listed against him.

U.S. District Judge Philip Pro has been assigned the case.