|Scene of a previous bomb blast in Nigeria|
At least 48 people were killed on Monday after an explosion ripped through a school in northeast Nigeria, as students gathered for morning assembly before classes began, Telegraph news reports.
Some reports suggested that the bomb was carried in the backpack of a suicide bomber, dressed as a student.
A teacher at the school, a medic and a rescue worker said that blast happened at the Government Comprehensive Senior Science Secondary School in Potiskum, Yobe state.
The rescue worker told AFP that 13 bodies had been taken to hospital with more than 30 others left "with various degrees of injuries". There was no official death toll.
"The students had gathered for the morning assembly when something exploded in their midst with a thunderous sound at exactly 7:50 am (0650 GMT)," added a teacher, who asked not to be identified.
"The explosion has affected many students but I can't say how many because we are now evacuating the victims to the hospital which is just 100 metres away," the teacher added, sobbing.
A medic at the Potiskum General Hospital, where the victims were taken, said scores of students had been admitted.
"We are still receiving casualties from the school which is a stone's throw from here," the medic said.
"Our priority now is to save the injured, so we have not started a headcount of the victims."
A local resident, Adamu Alkassim, said there was confusion in and around the school. The scene was a mass of abandoned footwear and blood.
There was no immediate claim of responsibility for the attack, but Boko Haram militants are likely to be the prime suspects.