Twelve security personnel were killed and ten others injured, five of them critically, in an explosion during a search operation near Baniadih village of Chatra district on Saturday.
Inspector General of Police Rajeev Kumar said the dead included nine Central Reserve Police Force personnel and a sub-divisional police officer.
official sources said the injured were airlifted to Ranchi for treatment.
Kumar, who had earlier said it was a landmine blast, later stated that prima facie it seemed the explosives were hidden in a box which exploded during a search.
Chatra is a Maoist-affected area and the joint team of the police and CRPF had launched the search operation last night.