Media reports have suggested the 14-year-old was stabbed
A 15-year-old student in Germany has been arrested on suspicion of killing a fellow pupil at school.
Police in Dortmund said emergency services were called to Kaethe Kollwitz comprehensive school in the town of Luenen, north of the city, on Tuesday morning.
Reports in German media say a 14-year-old was stabbed. Paramedics were unable to resuscitate him, officers said.
Neither of the boys have been officially identified.
The suspect, who holds German and Kazakh citizenship, was arrested shortly after the incident.
Police say the investigation into the circumstances of the death are ongoing.
In a joint statement, police and the public prosecutor urged social media users not to spread rumours about the attack.
The victim's relatives, as well as his fellow students and teachers, are receiving psychological counselling, officers said.