Undercover officers took to the streets of East Palo Alto today in an effort to arrest alleged buyers of crack cocaine.The operation “Buyer Beware,” the first of its kind in the city in more than five years, began early this afternoon and had netted three arrests by 3:40 p.m.About two dozen officers from the San Mateo County Probation Department, East Palo Alto police, Menlo Park police and the San Mateo County Narcotics Task Force, half of whom worked undercover, participated in today’s operation.Officers staked out the East Side Market at Clark Avenue and Bay Road, where some posed as dealers and others watched from nearby. The market is around the corner from a drug rehabilitation center called Free At Last.The message the officer hoped to send today is that “it’s not safe to purchase narcotics in East Palo Alto,” said East Palo Alto police Capt. Carl Estelle. “It fuels violence in all areas.”Possession of any amount of crack cocaine is a felony, according to East Palo Alto police Sgt. Renaldo Rhodes.