At least 17 children and a teacher were killed when the roof of a private school collapsed in Peshawar, Pakistan, on Thursday, police said.

More than 40 people were injured, Peshawar Capital City Police chief Mian Saeed said. The school is in Dir Colony in the inner city of the capital of Khyber Pakhtunkhwa province.

Lady Reading Hospital spokesperson Muhammad Asim said an emergency was declared at the hospital to treat the injured. All the children killed were aged 13 or younger, he said.

Rescue officials said 25 injured children had been taken to medical facilities. Teams were clearing debris and searching for children and staff who might still be trapped.

Prime Minister Shehbaz Sharif expressed grief over the deaths and directed the authorities to provide the injured with the best possible treatment.

The cause of the collapse has not been announced.