WALNUT CREEK (CBS-SF) — Investigators were searching for a masked gunman Wednesday who strolled into a Walnut Creek Valero gas station and fled with an undisclosed amount of cash, authorities said.

According to the Walnut Creek police the armed robbery took place at 4:35 a.m. at the  Valero station located at 605 Ygnacio Valley Road.

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Officers arrived at the station moments after the gunman fled but a search of the surrounding area with a police K-9 failed to turn up any trace of the suspect.

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Investigators described the gunman as an male, 30 years of age, standing 5-foot-9 with a stocky build. He was wearing blue jeans and a full face ski mask. The suspect was armed with a black handgun.

The suspect was believed to be the same person responsible for recent robberies in Redwood City and San Leandro. Investigators from all involved agencies were working together to get the suspect identified.

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Anyone with information is encouraged to call WCPD Detective Jeha at (925) 256-3518.