At least 20 people were killed and 15 others critically injured in eastern India on Wednesday when a minibus crashed into a tree and fell into a ditch, police said. The accident took place in the Gobindpur area of Jharkhand state, according to police officer Binod Kumar. The area is about 215 miles (350 kilometers) southeast of Patna, the capital of neighboring Bihar state. Initial investigations suggest the driver may have fallen asleep at the wheel, Kumar was quoted as saying by the Associated Press. All 40 passengers in the private minibus were part of a wedding party, but the bride and groom were not on board, Kumar said. The other five passengers also suffered minor injuries. All the injured were taken to a local hospital.