A plastic bag was thrown into the bin of a supermarket in southern Nigeria on Wednesday, triggering a massive explosion in a crowded market.
The incident happened in the district of Kano, in Borno state, at around 5:30am local time (20:30 GMT).
The blast injured two people, according to local media.
The explosion was heard from hundreds of metres away.
It left a crater 15 metres wide, the Associated Press news agency said.
No injuries were reported.
The local police told the AFP news agency that there was no immediate indication of any link to Boko Haram, which has carried out attacks on towns and cities across the northeast.