Witnesses say an explosion Thursday at a bus station on a busy road in northeastern Nigeria has killed more than 30 people, inclduing five soldiers, at the Mararaba-Mubi junction, in Adamawa state.

VOA's Hausa Service reports that authorities are unsure whether the explosion was an accident, possibly caused by a soldier carrying a bomb, or an attack by a suicide bomber.

The security source and witness Abubakar Adamu, a mechanic who narrowly avoided being blown up himself, said the blast set several busses on fire at the Marabi-Mubi junction, in a part of the country plagued by violence linked to the Boko Haram Islamist insurgency. "There were bodies everywhere on the ground," Adamu said.

Adamawa is one of the states where the Nigerian government is battling militant group Boko Haram.

The militants seized the town of Mubi last month as part of its campaign to create a strict Islamic state in northeastern Nigeria. The army has since retaken the town.

The blast location is about 30 kilometers west of Mubi, a town near the Cameroon border seized last month by Boko Haram militants fighting to carve an Islamic state out of religiously-mixed Nigeria. It has since been recaptured. Nigerian authorities, who rarely remark on security developments in the troubled northeast, did not immediately respond to requests for comment.

There was no claim of responsibility, but suspicion is likely to fall on Boko Haram, whose campaign to create an Islamic caliphate governed by sharia law has killed thousands since 2009. Continuing insecurity is a headache for Nigerian President Goodluck Jonathan ahead of February 2015 polls in which he is seeking a second elected term in office.

He has asked parliament for approval to extend an 18-month-old state of emergency in the northeast. Two female suicide bombers killed at least 44 people on Tuesday in the northeastern city of Maiduguri, medical officials said.

Some information for this report came from Reuters.