The U.S. Department of Labor has recovered $5.5 million in back wages for New Jersey gas station attendants who were not paid the required minimum wage or overtime in the last five years.

"Our investigations of the New Jersey gas station industry found widespread violations of the federal Fair Labor Standards Act's minimum wage, overtime, and record-keeping provisions," Mark Watson, the regional head of the department's Wage and Hour Division, said in a news release.

From the 2010 to 2014 fiscal years, the Labor Department has run a "multiyear enforcement initiative" that led to back wages and damages awarded to more than 1,100 employees, the department said Thursday.

Gas station employees are supposed to receive at least the federal minimum wage of $7.25 an hour and, for every hour worked beyond 40 in a week, overtime pay of time and a half.

"Our efforts are having an impact on the industry," Watson said.

The department recovered nearly $300,000 last year, which was the lowest amount since the 2010 start of the crackdown.

Other evidence of the crackdown's effects, the Labor Department said: gas stations hiring more employees to avoid needing overtime, using time clocks to track hours worked, and requesting training from the department regarding overtime and minimum-wage laws.

The gas station investigations and education campaign are continuing in 2015, the Labor Department said.

A spokeswoman said the investigation began because the department "has found issues in this industry in the past."

Local gas stations caught include BP stations in Burlington, Pennsauken, Maple Shade, and Mount Ephraim, according to data provided by the Labor Department.

In Burlington County, the gas stations have paid $3,820; Camden County gas stations have paid $3,381.

The crackdown hasn't uniformly blanketed the state. Some counties, including Gloucester, Atlantic, and Salem, have not seen gas stations pay out money, while Morris County gas stations have paid out more than $1.5 million.

Those payments also include damages, as employees are generally eligible for liquidated damages equal to their back wages, the Labor Department said.