Allied naval forces searching for enemy submarines in Strait of Messina according to the Kriegsnachrichten of the Chef des Admiralstabes der Marine dated Berlin 9 August 1917

An item referred to an agent reporting that on 28 July both sides of Strait of Messina during about a hour were illuminated with a large number of search lights. Motor boats and torpedo boats were search for an enemy submarine.

Source

Bundesarchiv RM-40-622