Asplundh, the Willow Grove, Pennsylvania-based landscaping company--one of the largest in the industry nationwide--must pay a $95 million fine for intentionally recruiting and employing undocumented workers over a period of four years, according to the U.S. Attorney's Office.

The fine for Asplundh Tree Expert Company comes after the company recently pleaded guilty in federal court in Philadelphia. The fine is the largest ever for an immigration case, according to prosecutors.

The practice carried on from around 2010 through December 2014, according to the U.S. Attorney's Office. During that time, the highest levels of Asplundh management remained “willfully blind" while supervisors and foremen hired undocumented individuals.

Many of the workers that were hired were being rehired, after Homeland Security investigations determined that they were unauthorized to work in the United States, authorities said.

Prosecutors said hiring undocumented individuals allowed the company to have a workforce that was "readily available and at their disposal" and maximized the company's productivity and profit.

It's unclear exactly how many undocumented individuals were employed by Asplundh, which was described by authorities as the "industry leader" in tree trimming and brush clearance.

Three Asplundh supervisors, including a vice president and managers, have already entered guilty pleas for felony conspiracy to commit fraud and misuse visas, the U.S. Attorney's Office said.