WASHINGTON — The Justice Department is stepping into a lawsuit against the company that handled background checks of National Security Agency leaker Edward Snowden and Navy Yard shooter Aaron Alexis.

The lawsuit alleges that the company, United States Investigations Services, engaged in a practice known at the company as “dumping” – failing to perform quality-control reviews on background investigations as a contractor for the White House Office of Personnel Management.

USIS dominates the background check industry, taking in $195 million in government payments last year for handling more than 45 percent of the government’s background checks.

A whistle-blower who is a former employee of USIS is suing the company on behalf of the government, and the Justice Department is joining the case.

USIS was involved in a background investigation of Snowden in 2011 and one of Alexis in 2007, but those particular jobs don’t figure in the lawsuit. OPM says it believes the file on Alexis was complete and in compliance with all investigative standards.

“The behavior by a small number of employees alleged in the complaint is completely inconsistent with our company values, culture and tradition of outstanding service to our government customers,” the company said in a statement. USIS “has taken these allegations seriously since they were first brought to our attention.”

The lawsuit was filed in July 2011 by whistle-blower Blake Percival. He charged that in an effort to meet revenue targets and maximize profits, USIS used a proprietary computer software program that automatically released background investigations to OPM that had not gone through the full review process. The lawsuit says the alleged “dumping” process was spearheaded by the vice president of field operations at USIS and by the company’s director of production control.

OPM had turned to private security screeners in the late 1990s because of growing backlogs that were snarling the government’s hiring process.

Under its contract with the government, USIS is required to conduct fieldwork on prospective applicants seeking federal employment, and trained reviewers from USIS are required to ensure conformity to OPM standards.

USIS is based in Falls Church, Va. The lawsuit was filed in federal court in Montgomery, Ala.