At least four people were injured in a blast in a private bus in Haryana's Fatehabad district on Tuesday, police said.The injured were taken to the government hospital in Fatehabad. The bus was travelling from Jakhal Mandi in the district to Fatehabad town; the blast occurred at a place called Bhuna, the police said.This is the third blast in Haryana in the last one month.Earlier, a blast took place in an empty railway coach in Panipat district.Last week, a low intensity blast in a moving Haryana Roadways bus left eight people injured.