– Maria Leon, a single mother of three, says she worked for years in two Chicago restaurants for less than the city’s minimum wage.

Last year, she sued the restaurants, which have the same owner, alleging they were violating city, state and federal wage laws. The two sides settled, but Leon believes it’s important to speak up on the matter.

“You can’t be silent. There are a lot of businesses who are doing this and we just sit there and take it because we need to work. But there are laws in place to protect workers,” Leon said.

Enforcement of Chicago’s minimum wage ordinance — which passed on Dec. 2, 2014, and gradually raises the wage to $13 an hour by 2019 — remains a work in progress. Some legal rights activists and labor experts say the city needs to dedicate more staff and resources to recovering wages for underpaid workers and holding businesses accountable. City officials say they’ve shifted to a more aggressive approach this year and results will prove out over time.

But there’s also this loophole: The city considers nearly 100 professions, including private security firms, to be exempt from the city wage ordinance because they’re regulated by the state. That means those businesses have to pay workers only the Illinois minimum wage, $8.25 an hour, instead of the city’s, which is currently $11 an hour.

That was news to the state.

The Illinois Department of Labor “is just learning of the city’s new interpretation of its own local minimum wage ordinance. Should the city decide to exclude certain workers, the state minimum wage still applies,” Ben Noble, spokesman for the department, said in an e-mailed statement.

City officials, meanwhile, say they’ve been interpreting the ordinance this way all along. As a result, dozens of wage complaints filed with the city against state-regulated businesses haven’t led to investigations.

About 550 complaints about minimum wage violations have been filed with Chicago’s Department of Business Affairs and Consumer Protection since the law went into effect in July 2015. Only about 140 have led to investigations. People who make initial complaints with the city often don’t follow up with the necessary paperwork to trigger an investigation, according to data provided by the city.

The fact that only 1 in 4 complaints are investigated is “troubling but not surprising given the squeeze-down on public resources and budget problems,” said John Bouman, president of the Chicago-based Sargent Shriver National Center on Poverty Law, who co-chaired the task force appointed by Mayor Rahm Emanuel to look at raising the city’s minimum wage in 2014. “It’s not magic,” Bouman said. “You gotta pay for this stuff.

“The employers know that they have a workforce that is intimidated for one reason or another — they need to work, so they’re unlikely to make waves,” Bouman said. “So they cheat them.”

For the first two years, the city was more focused on educating businesses; beginning this year, that approach has shifted to more aggressive enforcement, said Deputy Commissioner Barbara Gressel. To date, the city has recovered more than $213,000 in lost wages for underpaid workers but has not fined companies. That too could change, she said.

“It’s time for the gloves to come off,” she said.