On 14 January 1917, "Tsukuba" exploded while in port at Yokosuka. Some 200 crewmen were killed immediately, and over 100 more were drowned as the cruiser sank in shallow waters within twenty minutes, with a total loss of 305 men. The force of the explosion broke windows in Kamakura, more than twelve kilometers away. At the time of the disaster, more than 400 crewmen were on shore leave, which is why so many survived. The cause of the explosion was later attributed to a fire in her ammunition magazine, possibility through spontaneous combustion from deterioration of the Shimose powder in her shells.