Ananthapur (Ap), Oct 03: Suspected People's War Group (PWG) naxals blasted a telephone exchange with explosives last night at Yellore, about 70 kms from here. A group of 10 armed naxals entered the exchange, asked the watchman to vacate it and blasted the building using explosives, police said here today. Neither the identity of the ultras nor their motive was immediately known, police added. Bureau Report