At least four passengers were killed and eight injured when the Delhi-Dibrugarh Rajdhani Express derailed at Golden Ganj station near Chapra early Wednesday.12 coaches were derailed in the incident at around 0200 hours on Wednesday, Railway spokesperson Anil Saxena said. Five coaches-B-1, B-2, B-3, B-4 and pantry car-overturned in the derailment while seven other coaches-B-5 to B-10 and power car-got derailed at the station, about 75 kms from Patna, he said.