U.S. prosecutors have been investigating Japan's Mitsubishi UFJ Financial Group Inc. since late last year on suspicion of breaking regulations that prohibit money laundering in relation to North Korea, the New York Times reported Wednesday.

A subpoena was issued for MUFG after the state of New York said the group had intentionally ignored an internal filter meant to keep it from doing business with companies and people on international sanctions lists, the paper said in its online edition.

The state's Department of Financial Services reportedly said the group had also failed to set up a system to check the identities of some of its Chinese customers doing business along the North Korean border — a hot spot for money laundering.

It was not clear whether prosecutors had found any evidence that North Korea laundered money through MUFG, but the holes in the system designed to trace such transactions were a chief concern of the department, the paper added.

In 2013, the New York state regulator fined MUFG's banking unit $250 million for removing information from its records about transactions that involved parties in states like Iran and Myanmar. It also fined the unit a year later an additional $315 million for trying to hide information about that misconduct.