The charges involving the railroad come at a time when public workers’ unions across the country have faced heavy criticism for negotiating pension obligations that led many government agencies to slash services and lay off teachers, police officers and other workers.

A sampling of hundreds of cases approved by two doctors showed that $121 million had been paid to workers whose disabilities were either fabricated or exaggerated, according to court papers, though the total was quite likely more. It was unclear if officials would try to stop the payouts, or could even legally do so, before the disbursements hit $1 billion.

The federal investigation followed reporting by The New York Times for a series of articles published in 2008 that revealed systematic abuses of federal Railroad Retirement Board pensions by Long Island Rail Road workers.

The claims of disability made by the seven people charged with obtaining their pensions fraudulently contrasted sharply with their lifestyles, according to court papers. One of the defendants, Gregory Noone, 62, of East Islip, N.Y., who receives $105,000 in pension and disability payments each year, plays tennis several times a week and played golf 140 days over the course of one nine-month period, despite his reports that he had severe pain when gripping objects, bending or crouching, the complaint filed in the case said.