Firefighters on scene of grass fire on Berryessa Knoxville Road, Spanish Flat

(KRON) -- Firefighters in Napa are responding to a grass fire near Oak Shores Day Use Area on the 5500 block of Berryessa Knoxville Road, Spanish Flat Wednesday afternoon. According to CalFire, the blaze has grown to 4 acres with a moderate rate of spread.

Fire officials urge anyone traveling in the area, which is about 4 miles from Lake Berryessa Marine Resort, to use caution. There was no immediate word on whether structures were threatened as a result of the blaze.

Fire officials have dubbed the blaze the Smittle Fire.

This is a developing story. Check back for updates.