The copper thefts have resulted in multiple power outages including one at UCSF's Mount Zion hospital last week at Post and Divisadero Streets.
Police say the thieves strike between 2:00 and 6:00 in the morning.
They say the suspects' park near a manhole cover, remove the cover, climb down in the vault and cut one inch thick copper wires.
Anyone who witnesses suspicious behavior around underground vaults is asked to call 911.
