The headquarters of Booz Allen Hamilton in McLean, Va. (Kevin Lamarque/Reuters)

Shares in Booz Allen Hamilton Holding Corp. tumbled in after-hours trading Thursday after the Northern Virginia-based consultant disclosed through a filing with the Securities and Exchange Commission that its billing practices were under investigation by the Justice Department.

The company’s stock fell about 12 percent.

The firm said in a statement on its website that the Justice Department informed it this month that it was “conducting a civil and criminal investigation relating to certain elements of the company’s cost accounting and indirect cost charging practices with the U.S. government.”

“To date, our internal and external audit processes have not identified any significant deficiencies or material weaknesses, or identified any significant erroneous cost charging,” Booz Allen said. “The company is cooperating with the government in these matters and expects to bring them to an appropriate resolution.”

The company had no further comment.

McLean-based Booz Allen employs more than 23,300 people and had revenue of $5.80 billion for the 12 months that ended March 31, according to the company’s website.

As a government contractor that sells billions of dollars in services to U.S. spy agencies, Booz Allen is closely watched. It was thrust into the spotlight in 2013 when former employee Edward Snowden acknowledged leaking government secrets. The company again came under scrutiny in 2016 when another Booz Allen employee working with the National Security Agency was charged with stealing classified information.

Booz Allen was once owned by the Carlyle Group, a District-based private-equity firm that bought it in July 2008 and took it public in November 2010. Carlyle sold its last stock in Booz Allen late last year.

Booz Allen has been a Washington fixture for years, employing thousands and providing management and consulting services to the government, particularly the defense and intelligence agencies.

It is a leader among the contractors supplying tens of thousands of intelligence analysts to the government, including technologists such as Snowden.