At least 33 pupils and a teacher have been killed after a school roof collapsed in the north-western Pakistani city of Peshawar, according to hospital officials.

More than a dozen others are injured, with some in a critical condition.

Emergency services were called to the private Al-Khair school in Dir Colony at 08:48 (03:48 GMT) on Thursday after lessons had begun, rescue official Bilal Faizi told the BBC.

The roof of an upper-floor classroom had collapsed, he said, causing ceilings below to cave in and trap children beneath the debris.

Announcing the arrest of the school's owner, police chief Mian Saeed promised a thorough inquiry into "whether there were any violations of building codes".

Warning: This article contains distressing details

An English teacher from a nearby school said he immediately rushed to the site with other local residents when they heard sirens and the sound of ambulances.

Together, they pulled more than 20 children from the rubble, he said.

"I personally pulled out six children with my own hands. Most of them were alive and talking. But later it was found that they had passed away."

"There was a lot of blood," he said. "One child said he was in a lot of pain. His tongue had dried up in his mouth, [and he was] asking for water."

Sohail, another local resident, said he and others tried to remove children from under the rubble "using shovels".