The number of investigators at the US Labor Department who enforce child labor, minimum wage, and other workplace laws fell to a historic low this month, sparking concerns about the government's ability to police wage theft.

The Wage and Hour Division had 611 investigators as of mid-May, according to data obtained by Rutgers University and Northwestern University, a loss of about 39 since the end of last fiscal year. That figure is the lowest recorded since 1973, according to DOL data.

The wage division oversees 11 million workplaces and 165 million workers.