QUETTA - House of Principal Polytechnic Institute was attacked with a hand grenade at Sariab Road here on Thursday, police said. Unidentified people lobbed grenade on the house of Ghulam Rasool Mengal, Principal Polytechnic Institute, located at Lehri Street of Sariab Road. Grenade landed in courtyard of the house and went off with a big bang. Windowpanes of the house were scattered and a vehicle was damaged due to grenade blast. Soon after the blast, police and personnel of other law enforcement agencies rushed to the site and cordoned off the area. In another incident, a locally made explosive device, planted by unidentified people with wall in Jail Muhalla in Zhob district exploded and damaged the wall. However, no loss of life was reported in the blast. Meanwhile, police recovered a rocket shell from Satellite Town area of Quetta and later defused it. Police said that some children were picking garbage when they spotted a rocket shell and later area people informed the police. At this, police and personnel of Bomb Disposal Squad rushed to the site and defused the rocket shell.