Inspector-General of Police V Deshmukh said the police jeep overturned due to the impact of the clamour bomb blast in Jaranga village in the district.
All the injured have been admitted to a hospital in Ranchi.
The Maoists also blew up a middle school, Anant Madhya Vidyalya, at Pratappur in Chatra district last night after placing dynamite in class rooms.
The school was among the places where voting was to be conducted on December 18 for the assembly polls in the state, police said.
This was the fourth school in three days to have been blown up by the Maoists. On Tuesday, they had demolished two schools in Palamau district and one in Giridih district.
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