The cause of a fire, that burned about an acre of vegetation in Watsonville yesterday afternoon, is still being investigated. The blaze, which broke out behind the 500 block of Ohlone Parkway, charred dry grass, brush, and a stand of eucalyptus trees before firefighters got it under control. Reportedly, no structures were damaged and no firefighters were injured (in the brush fire that broke out around 1:30 p.m).