The company operating the District’s fast-growing bicycle-sharing network may have underpaid some of its employees for more than two years, a former employee has alleged.

Former employee Samuel Swen­son has told the U.S. Labor Department that he was paid $13 hourly for work that should have been subject to the federal “bicycle repairer” rate of $14.43 hourly or “truck driver, light” at $15.66 hourly. Before he left Capital Bikeshare, Swenson said, he received a raise to $15 hourly but was not paid fringe benefits required under federal law.

The bicycle-share contractor is “doing a good thing by creating green jobs, but they need to play by the rules,” Swenson said.

Capital Bikeshare, a subsidiary of Alta Bicycle Share of Portland, Ore., operates the system under a 2010 contract with the District’s Transportation Department worth up to $16.4 million over five years. The contract specifies that Capital Bikeshare must follow federal “prevailing wage” determinations, which are published regularly by the Labor Department.

Joanna P. Hawkins, a deputy regional director with the U.S. Labor Department, said the agency has an “active, open investigation” of Capital Bikeshare underway. But she declined to provide details on the probe, which is being conducted by the department’s Wage and Hour Division.

A Capital Bikeshare station is seen at 5th and F Streets NW. (Sarah L. Voisin/The Washington Post)

Mia Birk, Alta Bicycle Share’s vice president, said the firm is “reviewing the inquiry from the Department of Labor and cannot comment at this time.”

The D.C. Transportation Department has been approached by Labor Department investigators, spokeswoman Monica Hernandez said, and is cooperating with the inquiry. “For us, it’s very important that we maintain our partnership in place with the federal government,” she said. “We will work with our vendor to make sure they are indeed paying what federal law requires.”

Ari Weisbard, advocacy director for the D.C. Employment Justice Center, said many of those working for federal and District contractors are not aware of the prevailing-wage requirements, set out in the 1965 Service Contract Act.

“They’re important to ensure that federal government and taxpayer dollars are used to create quality jobs rather than bargaining rates down to where workers can barely get by,” he said. “It’s something that we have been trying to get more attention to.”

The Capital Bikeshare network has grown steadily in size and popularity since its September 2010 debut. Although the network has stations in Arlington County and Alexandria and a major expansion to Montgomery County is expected soon, the vast majority of trips are taken in the District.

As of March, the system had more than 32,000 annual members, and 267,000 had purchased short-term passes since the system launched. Capital Bikeshare is the largest active system in the United States and the largest operated by Alta. The firm is preparing to launch larger systems this year in Chicago and New York City.