The request to keep investigative details under wraps could complicate the car maker’s efforts to provide answers to shareholders, dealers and car buyers. The Justice Department has told lawyers for the firm that making any interim findings public would hamstring efforts to pursue potential criminal charges and a multibillion-dollar fine, according to people familiar with the matter.
As recently as last month, Volkswagen had promised to make public details of an investigation being conducted on the company’s behalf by the law firm Jones Day. The investigation is still ongoing and not yet nearing completion, said people familiar with the matter.
Volkswagen admitted last September to installing so-called defeat-device software on certain diesel-powered Audi, Jetta, Golf and Passat vehicles, allowing them to pollute more on the road than during government emissions tests.
"The Jones Day investigators are sifting through enormous amounts of data," Europe’s largest car maker said on March 2. "Volkswagen will report preliminary results of the investigation in the second half of April."
At the time, Volkswagen said 102 terabytes of data had been secured by its investigators, the equivalent of about 50 million books.
On Tuesday, Volkswagen told The Wall Street Journal that it is uncertain about its public disclosures regarding the investigation. "Concerning the communication about the investigation of the diesel topic, we are currently in intensive discussions," the company said in a statement. "We will comment further in the second half of April."
The Justice Department is concerned that if certain names or facts are made public, it could make it more difficult for civil and criminal authorities to determine what happened, according to people familiar with the conversations. Employees or witnesses identified by the company might become reluctant to talk, for example, the people said.
The company has said it would brief its board Friday and report results of the Jones Day investigation into how 11 million cars world-wide were equipped with software to dupe emissions tests.
The delay comes as Volkswagen is embroiled in legal proceedings in the U.S. and Germany, including criminal investigations into fraud allegations, more than 500 civil lawsuits and a U.S. Federal Trade Commission inquiry into whether Volkswagen’s advertising for "clean diesel" constituted fraud in advertising.
The request from the Justice Department isn’t a formal order, but it puts pressure on the company to comply. Companies viewed as uncooperative by the department can face harsher penalties in resolving any charges.
The new development is the latest indication that the car maker won’t be able to quickly move beyond the scandal that has consumed it since last year.
Volkswagen has already postponed the publication of its 2015 earnings twice and delayed its annual shareholder meeting. The company is now scheduled to release its full-year earnings report on April 28.
Last month, Volkswagen sought an extension on a court-imposed deadline to provide an update on how the company plans to fix the emissions software in existing cars. For now, the auto maker still faces a Thursday deadline to reach an agreement with regulators on a fix and report it to the court, but it is unclear if it will meet that deadline.
A spokeswoman for the Environmental Protection Agency, which made the allegations against the company public in September and is working with the company to come up with a solution, declined to comment.
In response to a civil lawsuit in Germany, Volkswagen has said the diesel-engine software was calibrated to cheat by a small group of engineers in 2006 without the knowledge of top executives. But it said its senior executives were aware of the so-called defeat devices for nearly a year and a half before admitting their existence to U.S. regulators.
The withholding of additional details could help the government avoid the criticisms it faced following an earlier auto industry investigation. When General Motors Co. released a report in 2014 amid a federal probe into how it handled problems with its ignition switches, it led to tough questions about why the government decided against charging any of the individuals identified by investigators as knowing about the problem.
General Motors admitted to criminal wrongdoing last September and paid $900 million to resolve charges that it schemed to conceal the deadly safety defect from U.S. regulators. No individuals were charged in connection with the investigation.
Devlin Barrett and Aruna Viswanatha, The Wall Street Journal. William Boston contributed to this article