RIO DE JANEIRO, May 8 (Xinhua) -- A homemade bomb exploded Friday at a public school in Belford Roxo, a city in Rio de Janeiro state, injuring at least 10 students, local authorities said.
Belford Roxo Mayor Mariana Malta said the device detonated after a student found it on campus and threw it into the air.
The school said the situation has been brought under control, and the injured students, aged 13 to 15, were discharged from a local hospital after receiving treatment.
Local television reports said the homemade bomb was filled with sand and packed with nails, nuts and bolts that were ejected in the blast.
Police officers conducted a thorough search of the school and ruled out the presence of any other explosives.
An education official of Rio de Janeiro state said authorities are jointly investigating how the bomb was brought into the school.
