A pipe bomb exploded inside a mailbox and another device was blown up in a controlled explosion, officials said Saturday.
There were no injuries.
San Diego Sheriff's Deputy Lt. Tony Giammarino said a resident reported at about 9 a.m. that a mailbox had been destroyed.
Deputies at the scene found a second bomb nearby and a bomb-disposal team exploded the device in a field.
Bonsall is an unincorporated community in north San Diego County.