The government is using the Financial Institutions Reform, Recovery and Enforcement Act to issue the civil subpoena, a 1989 law used in investigating large financial institutions, said the source who requested anonymity, citing the sensitivity of the ongoing probe. The law allows the government's civil division to investigate fraud over the last 10 years.
VW spokeswoman Jeannine Ginivan declined to comment on talks with regulators, but said the automaker "will continue to cooperate with all relevant government agencies."
The Wall Street Journal reported the subpoena earlier Tuesday. The law has been used to subpoena auto loan finance companies in recent years, among other companies.
VW faces investigations around the world after it admitted in September to installing software in up to 11 million vehicles that allowed them to emit up to 40 times legally allowable pollution in real world driving.
Last month, a federal judge imposed a March 24 deadline for Volkswagen to state whether it has found an emissions fix for 600,000 U.S. diesel vehicles that is acceptable to U.S. regulators.
The U.S. Justice Department in January sued Europe's Volkswagen for up to $46 billion for violating U.S. environmental laws. VW and its Audi and Porsche brands are barred from selling any new 2016 diesel models in the United States. VW also faces more than 500 lawsuits from U.S. owners.
Settlement talks are still ongoing between the Justice Department, EPA and California Air Resources Board that could include buyback offers and fixes for vehicles.