A majority of the roughly 90 blue-collar restaurant workers serving the U.S. Senate were improperly classified by their private employer, a top U.S. Capitol administrator told a congressional committee last week, putting them at risk of being underpaid and prompting a Labor Department inquiry into the matter.

The workers employed by Restaurant Associates have sought higher wages for more than a year, and a December contract renegotiation appeared on its face to deliver better pay and benefits. But several workers said they were subsequently reclassified into new, lower-paying jobs, thus cheating them out of the raise they were expecting.

One worker, for instance, told The Washington Post in January that he had gone from being a cook to a “food service worker,” a classification that meant the difference between $13.80 an hour and $17.45 an hour.

Architect of the Capitol Stephen T. Ayers told a Senate Appropriations subcommittee on Tuesday that the misclassifications were more widespread than previously known.

“We thought we were doing a good thing only to be surprised only a week or two later to learn that the pay rates we agreed to were not going to be paid,” Ayers said at the hearing last week.

Soon after the renegotiated contract went into effect in mid-December, Ayers said, it became clear that a handful of employees had been misclassified — raising suspicions about a more pervasive problem.

Ayers’s deputies then interviewed 86 of the cafeteria and restaurant employees. That inquiry determined that 35 employees were classified properly, said Laura Condeluci, a spokeswoman for Ayers; the other 51 were not.

Restaurant Associates immediately reclassified 35 of the 51 misclassified workers and delivered back pay, leaving 16 in dispute, Ayers said. Half of those are being resolved through negotiations; the rest have been referred to the U.S. Department of Labor for resolution.

At the hearing, Sen. Brian Schatz (Hawaii), the ranking Democrat on the legislative branch subcommittee, said, “In my opinion, Restaurant Associates improperly, intentionally and systematically misclassified employees,” and he pressed Ayers on whether he believed the company was living up to the terms of the contract.

“This misclassification, it seems to me, is not in compliance with the contract,” Ayers said.

A Labor Department spokesman did not respond to a question about the status of the probe. A spokesman for Restaurant Associates referred questions to Ayers’s office.

The wage dispute has simmered for more than a year and was pushed into the headlines last March when one Senate worker, Charles Gladden, came forward to say he was homeless. What has helped push the dispute toward to a resolution has been the interest from senators themselves, including Schatz and the subcommittee’s chairwoman, Shelley Moore Capito (R-W.Va.), who said Tuesday she was following the matter closely.

Organizers with Good Jobs Nation, a project of the Change to Win labor coalition, have sought to raise awareness of the Senate workers’ plight as part of their national campaign for a $15 minimum wage and the right to form a union for federal workers, and they have continued to watch the dispute closely.

Paco Fabián, a spokesman for the coalition, said the misclassification has had serious repercussions. One immigrant worker, he said, was unable to pay for a renewal of his federal work permit and has thus been unable to do his job in recent weeks. Fabián said the pay differential the worker is owed under the renegotiated contract would have allowed him to get the permit and keep working.

Fabián said the wage discrepancy “could mean missing meals, not paying bills and potentially losing a roof over their heads” for workers.

“There should be consequences for noncompliance in federal contracting,” he added. “If it’s happening right under the noses of lawmakers, then it’s likely happening all over the federal contracting system.”