At least 12 students were injured in an explosion at a school in Indian-controlled Kashmir on Wednesday, police said, though the cause of the blast was not immediately clear.

The Indian part of Kashmir, a Himalayan region divided between India and Pakistan, has been plagued by separatist violence for years, with clashes between security forces and militants killing more than 100 civilians over the past year.

But witnesses did not report any clash before the blast in a 10th-grade classroom at the Falai-e-Millat private school, just south of the state capital, Srinagar.

“We were studying and all of a sudden there was an explosion and we ran out and I saw my legs bleeding,” Faisal Ahmad, 16, told Reuters.

Police were investigating, a spokesman said.

A 13-year-old boy was killed and one injured in Kashmir last week after finding unexploded ordance after a clash.