Fast Trak, which is based in New Jersey, operates throughout the metropolitan New York area and has received financing in the past from Victory Park Capital, a private equity firm in Chicago, and J. Burke Capital, a Manhattan investment firm. Fast Trak was among the entities subpoenaed in the investigation.

A lawyer for Fast Trak, Larry Hutcher, said the firm had done nothing wrong and had potentially lost money through its involvement with the suits connected to the indictment.

“Our client has nothing to hide and is fully cooperating,” Mr. Hutcher said.

“Our client is confident that they have acted properly in all cases and in all instances,” he added. “If there was a fraud, we are a victim of this fraud.”

Several websites that Fast Trak has used to recruit customers have been inoperable for over a week. Mr. Hutcher said that the firm was still collecting on cases it had financed previously, but would not be financing new cases under the Fast Trak name. He said the move was unrelated to the indictment.

Unfettered by regulation in most states, litigation-finance firms have become entangled in past disputes. Some firms are being challenged for making high-interest advances to former professional football players waiting to collect awards in concussion litigation with the N.F.L.

Other firms worked with a cadre of doctors, lawyers and marketers in litigation involving pelvic mesh, paying for procedures for women involved in so-called mass tort cases against medical device manufacturers. Some women have said they were pressured into surgeries to remove pelvic mesh implants so that the lawsuits would be more lucrative.

The alleged slip-and-fall scheme has echoes of that approach. In the indictment, the authorities accuse the group of men of telling people that their personal injury suits would be dropped if they did not get medical treatments or surgeries. As an incentive, the people were “offered a payment after the completed surgery.”