Cal-Fire responded to a report of a brush fire 5 miles east of Jamul about 1:p.m. this afternoon. Upon their arrival the fire was about 10 acres and soon encompassed more than 300 acres. Additional fire units arrived from, Escondido, Viejas, Chula Vista, Vista, North County Fire, Pauma and various other county fire departments. Highway 94 east of Jamul has been shutdown to all traffic including residents. Otay Lakes Road has also been shut down. Cause of the fire has yet to be determined. At this time no structures have been reported as harmed.