Three brothers were killed in a bomb blast in Andhra Pradesh's Kurnool town on Tuesday, police said.The incident occurred near Nandyal checkpost on the outskirts of Kurnool when the three brothers, including two real estate developers, were surveying a piece of land which they had purchased sometime back.The deceased have been identified as J. Mallikarjuna, J. Rajasekhar -- both real estate businessmen and J. Sreenu, an Assistant Sub-Inspector of Police.Another person, identified as Sudhakar, a driver in the Survey Department, was injured.According to the police, the blast occurred when some waste material was set on fire by some workers. While two brothers died on the spot, Sreenu succumbed at Kurnool Government Hospital.The police suspect that country-made bombs were kept in the garbage. A police officer said an investigation is on to find out if somebody had concealed the bombs in the field or if they were deliberately planted to target the brothers.According to people living in the vicinity, the brothers were well-known in the town as they had executed several projects. They had purchased that piece of land for Rs 20 crore.