Bhubaneswar, June 11 : At least four persons were killed and another seriously injured in an oil tanker explosion in Odisha's Nayagarh district early on Saturday, police said. The incident occurred on a bridge over the river Kusumi around 2 a.m. near Badapandusara under Itamati police limits of Nayagarh. According to the police, two oil tankers were coming from Paradip and heading towards their destination drop-off points on the national highway connecting Nayagarh and Bolangir. Howver, one of the oil tankers plunged off the bridge into the river and three staffers of the second tanker came to rescue the injured driver and helper when the tanker exploded, the police said. The deceased were identified as Sameer Nayak, Pankaj Nayak, Dipu Khatua, and Chandan Khatua. All were local residents of Nayagarh. The injured person was first admitted to Nayagarh district headquarters hospital and later shifted to a hospital in Bhubaneswar. His condition is stated to be critical, the police said. /IANS