Kueblboeck was on a holiday cruise from Hamburg to NY, the dpa news agency and Bild newspaper reports.
Daniel Kueblboeck reportedly went overboard early on Sunday morning off the coast of Newfoundland.
Maritime Forces Atlantic says after 80 hours of searching the area covering 1,227 square nautical miles with four ships and two aircraft, there was no sign of 33-year-old Daniel Kueblboeck.
German media are reporting that Daniel Kueblboeck was on an Aida Cruises ship when he went overboard early Sunday near Newfoundland.
The dpa says Kueblboeck's management agency was not immediately available for comment.
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Kueblboeck was on the AidaLuna, which was due into St. John's on Sunday afternoon. It was reported that the ship sent an alert to the Canadian Coast Guard around 6 o'clock Sunday morning.
According to a Germany's DPA news agency source, the Canadian coast guard airplanes and helicopters took part in an intensive operation in search of the German singer.
A passenger was seen throwing himself into the sea, and the search of the boat then established that the singer was missing, the cruise line said.
Aida Cruises issued a statement confirming that Kueblboeck had jumped overboard.
Gough says the case has now been turned over to the RCMP as a missing persons investigation.