Denmark's largest bank is the object of scrutiny by U.S. law enforcement over allegations of money laundering flows from Russia and other states, The Wall Street Journal reported Friday, citing a person familiar with the matter.

The investigation, by the U.S. Justice Department, the Treasury Department and the Securities and Exchange Commission, is related to transactions at Danske Bank's Estonian branch over multiple years through 2015. The WSJ had previously reported the bank was looking at $150 billion of money flowing through accounts of non-Estonians at that branch.

A whistleblower complaint filed with the SEC more than two years ago identified Deutsche Bank and Citigroup as involved with transactions going into and out of the Danske Estonian branch, the WSJ reported. Deutsche Bank handled dollar wire transfers as a correspondent bank for Danske and Citi's Moscow office was involved in some of the transactions, the unnamed source told WSJ.

A spokeswoman for Citi had no comment, and a spokesman for Deutsche Bank also declined to comment. A spokesman for Danske Bank said by email to CNBC, "As a regulated business, we have interactions with authorities in various jurisdictions on an ongoing basis. However, as a general rule, we do not comment."

Danske began its own investigation into activity at its Estonian branch last year and is supposed to release a report on money laundering issues next week, the WSJ report said. The bank was already facing investigations by officials in Denmark and Estonia. In Estonia, officials were looking at more than two dozen former employees of the bank, including the former branch CEO. The former employees are accused of helping to launder $230 million from Russia.

Read the WSJ story here.