The defendants live in Washington, California, Nevada, Michigan and British Columbia.

Lawyers listed for 15 of the 23 defendants did not immediately respond to requests for comment on Tuesday, while another three declined to comment. Four of the defendants were still at large. Information about the remaining defendant’s lawyer was not listed in court records.

The U.S. Attorney’s Office for the Eastern District of Washington declined to comment further on the case on Tuesday, including to say how the defendants had been initially connected to each other.

According to the indictment, one of the defendants had discussed bringing a false misconduct complaint against the F.B.I. agent investigating the case. As part of that false narrative, the authorities said, that defendant would claim to the F.B.I. that his family was being threatened by the Mahdi Army, a militia group in Iraq.

In total, about 14 collisions were staged by the group, the indictment said. In one of them, the authorities said, one of the defendants intentionally drove a Toyota Sienna minivan into an Infiniti FX35, a crossover S.U.V. carrying several other defendants, including the driver, near an intersection in Franklin County in southeastern Washington in January 2019.

The minivan’s driver had boasted to the F.B.I. informant about the fraud scheme, investigators said.

“I did the insurance in the day and I hit it at night,” he said, according to the indictment.

In another collision, involving a Jeep Grand Cherokee and a Chevrolet Traverse in September 2019 in Pasco, Wash., a city in the southeastern part of the state, two of the defendants used hammers to inflict additional damage to the Jeep before the police arrived, the authorities said.

In April 2020, investigators said, one of the defendants rammed a Chevy Malibu three times into a second Chevy Malibu at an intersection in Kennewick, Wash.