"It is very routine procedure to examine whether they should have published an ad hoc," a Bafin spokeswoman said, referring to formal regulatory release protocol.

Bafin reviews hundreds such cases each year, a process which typically takes two to four weeks and can lead to a fine if the rules were violated.

German financial daily Handelsblatt on Friday also reported that Bafin was looking at the situation.

Deutsche Bank declined to comment.

(Reporting by Jonathan Gould, Editing by Edward Taylor)