The explosion on the USS YF-415, which occurred on March 7, 1968, was caused by an accidental detonation of a 500-pound bomb. This incident took place while the ship was operating in the vicinity of the naval base in Subic Bay, Philippines. The explosion resulted in significant damage to the vessel and led to the tragic loss of several crew members.

For further details, you can refer to sources that document naval incidents and the history of the USS YF-415.