This is the latest after-shock related to the 7.2-magnitude quake that rocked Baja California Easter Sunday and killed two people in Mexico.
Meanwhile, Governor Arnold Schwarzenegger is in Calexico Thursday, touring the quake damaged town for the first time.
He has already declared a state of emergency for Imperial County.
Calexico says it needs more than $12 million in federal and state funds just to repair its water treatment plant. The downtown business area remains off limits as officials try to determine which buildings can be re-opened.