The number of people killed in an explosion in a troubled tribal area of north-west Pakistan has risen to 32, local officials say.
Arab militants are reportedly among the dead, but officials denied claims made in Islamabad that Uzbek and Chechen militants were also killed.
Locals told the BBC that the site used to be a madrassa (religious school).
A BBC correspondent in the area says the building was being used as a training facility by Arab fighters.
Our correspondent says the bodies of those killed in the blast, thought to have been a missile strike, have buried by locals in North Waziristan.
Many were so badly mutilated by the blast they were impossible to recognise. Officials say that women and children may be among the dead.
The scene of the attack is deep inside North Waziristan, in an area which is controlled by the pro-Taleban militants.
A spokesman for the US-led coalition in neighbouring Afghanistan denied responsibility for the attack.
North Waziristan is seen as a safe haven for the Taleban
"I am not aware of any reports of missiles being fired from Afghanistan into Pakistan," said Lt Col David Accetta.
"Pakistan is a sovereign nation, and we respect sovereignty," he said.
Tuesday's attack has been condemned by the campaigning group, Human Rights Watch (HRW).
The group said Islamabad should launch an independent investigation into the strike, which the Pakistani army said was caused by explosives at the site.
The army said pro-Taleban militants died in the blast.
"The Pakistani government should immediately allow independent investigators and journalists access to the Datta Khel area of North Waziristan to ascertain exactly who and how many have died, at whose hands and under what circumstances," HRW South Asia researcher Ali Dayan Hasan said in a statement.
On Tuesday, local people told the BBC that an aircraft came, bombed the area and then went back to Afghanistan.
The apparent attack was said to have come from over the border at the village of Kalarai in the Shawal area of North Waziristan, about 40km (25 miles) west of Miranshah.
Last October, an air raid on a religious school further north in Bajaur agency left more then 80 people dead.
A number of other raids on suspected militant targets inside Pakistani territory have apparently been launched from over the Afghan border, although never confirmed.
Pakistan has been accused of allowing the Taleban safe havens along the border, after striking a number of controversial peace deals with militants in its tribal areas.