California Code, Government Code - GOV § 7475

An officer, employee, or agent of a state or local agency or department thereof, may obtain financial records under paragraph (3) of subdivision (a) of Section 7470 only if he obtains a search warrant pursuant to Chapter 3 (commencing with Section 1523) of Title 12 of Part 2 of the Penal Code. Examination of financial records may occur as soon as the warrant is served on the financial institution. Nothing in this chapter shall preclude a financial institution from notifying a customer of the receipt of a search warrant, unless a court orders the financial institution to withhold notification to the customer upon a finding that such notice would impede the investigation.

The financial records sought pursuant to this section by a search warrant shall be made available to an officer, employee, or agent of a state or local agency or department thereof within 10 days after the warrant is served on the financial institution unless prior to the expiration of such 10 days such institution makes a written showing to the court that issued the warrant that the records cannot reasonably be made available within the 10 days and that an additional period of time is required to make the records available. Upon such showing the court shall extend the period of time within which the records must be made available to whatever period of time is reasonably necessary.