MARTINEZ (CBS SF) — Contra Costa County firefighters say a one-alarm grass fire that broke out in Martinez Sunday afternoon was suspicious in nature.

The cause of the fire is undetermined, but Contra Costa County fire spokesman Steve Aubert said the recent rains have left the tule-filled area “pretty wet and pretty green.”

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The three spot fires were reported at 2:30 p.m. near Granger’s Wharf and firefighters contained the flames about one hour later.

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The scene was cleared by 5 p.m. and four engines, an investigator and a battalion chief responded to the incident.

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Martinez police said no structures were involved and the 100 block of Berrellesa Street was temporarily closed.