I have recently 'found' a few Italian ships that were lost with all hands and no trace during WWI:

The barque San Giuseppe (952 tsn), last seen February 7, 1916 in Nice while sailing from Philadelphia (from where she had sailed in December 1915) in Savona with a cargo of coal ;
The steamer Soperga (4034 GRT), which disappeared after leaving Norfolk (coming from New Orleans) on September 16, 1917, bound for Gibraltar ;
The steamer Salento (2591 GRT, 1891), seen for the last time off Spithead while en route from Hull to Civitavecchia and reported missing November 2, 1916;
The sailing ship Monte Carmelo (1686 GRT, 1883), which departed from Genoa on April 24, 1916 bound for Pensacola (in ballast) and seen for the last time in the Gulf of Mexico on June 29, 1916;
The steamer Maddalena (or Madalena) (2601 GRT, 1891), somwehere mentioned as probably mined on October 25, 1917 while sailing from Clyde/Milford Haven to Bagnoli;
The steamer Luigi Parodi (4158 GRT, 1899), seen for the last time January 23, 1915 off Cape Henry while en route from Baltimore to Augusta with a cargo of coal;
The steamer Iniziativa (2058 GRT, 1881), which departed from Swansea on November 10, 1915 bound for Civitavecchia with a cargo of coal, and disappeared ;
The brigantine Espero (135 tsn), which sailed from Viareggio on November 21, 1917, in ballast, bound for Carloforte, and disappeared ;
The steamer Audax (2106 GRT, 1889), which sailed from Greenock for Genoa on October 30, 1916 and was never seen again;
The barque Anna M. (tsn 817) which departed from Genoa for Baltimore on May 25, 1916 and disappeared;
The brigantine Angelo Ferrara (195 tsn) disappeared in 1917.


Has anyone ever investigated the possibility that any of them had been sunk by a U-Boot?