Police are seeking the public's help in finding a serial bank robber who is known to wear sports caps during holdups.

Authorities said the man is responsible for at least four bank robberies between April 2006 and March 2007.

The FBI said the robber waits in line for a teller, approaches and presents a demand note. To date, no weapons have been threatened or displayed during the robberies.

The robber is described as a white man in his mid-30s. He has a medium to heavy build, short dark hair and is about 5 feet 8 inches to 5 feet 10 inches tall. He also has a dark goatee.

Authorities said the robber was involved in the following bank heists:

    * Bank of the West, 1011 Helen Power Drive, Vacaville, on April 12, 2006, and Feb. 26, 2007
    * Golden 1 Credit Union, 6839 Five Star Blvd., Rocklin, on March 2, 2007
    * Washington Mutual Bank, 2011 Harbison Drive, Vacaville, on March 12, 2007

Investigators said the same robber may also have a connection to these bank robberies in Sacramento and Yolo counties:

    * Big Valley Credit Union, 2180 Golden Center Lane, Gold River, on March 5, 2007
    * Wells Fargo Bank, 340 F St., Davis, on March 10, 2007

Anyone with information regarding any of the above bank robberies may call the FBI in Sacramento at 916-481-9110, the Sacramento County Sheriff's Department at 916-874-5115, the Vacaville Police Department at 707-449-5200, the Rocklin Police Department at 916-625-5400, the Davis Police Department at 530-747-5400 or Crime Alert at 916-443-HELP.