"The investigation encompasses the period September 20, 2018 until February 20, 2019 and pertains to disclosure of insider information and the obligation to establish an insider list ... in connection with the disclosure of suspected money laundering within the company," Swedbank said in a statement.

Swedbank said it was assisting the watchdog.

Sweden's FSA in March fined Swedbank a record 4 billion Swedish crowns (351.57 million pounds)for serious deficiencies in its anti-money-laundering work and said the bank had withheld information from authorities.

Its shares were down 3% at 1142 GMT.

Shares in Sweden's oldest retail bank fell by a third last year after details of the scandal, which also engulfed Danish peer Danske Bank, emerged at the end of 2018 and through 2019.

Swedbank responded by firing its chief executive and much of its board.

(Reporting by Anna Ringstrom; editing by Helena Soderpalm and Jason Neely)