Islamabad, Pakistan (CNN) Militants raided a university in northwest Pakistan on Wednesday, timing their attack to a ceremony at the school to ensure maximum casualties.

After security forces combed the campus block by block after the massacre, Mehmood Khan, provincial home minister of Khyber Pakhtunkhwa, said 19 civilians were killed, along with four terrorists. He expects the number of civilian deaths to increase.

Earlier, an army spokesman said that 21 civilians had been killed.

The attack took place at Bacha Khan University in Charsadda, Peshawar, less than 40 kilometers (25 miles) from where the Pakistan Taliban slayed 145 people, including 132 children, in a school attack in December 2014.

It’s unclear whether the group was responsible for the Wednesday incident.

One Pakistan Taliban spokesman, Umar Mansoor, said the attack was in retaliation for military operations against the group. Mansoor was also the mastermind behind the December 2014 attack, Pakistan’s DawnNews reported.

But another spokesman, Mohammad Khurrassani, from the Pakistan Taliban’s central organization, disavowed any role.

We “strongly condemn the attack on Bacha Khan University in Charsadda and disown the attack, saying this is not according to Shariah,” Khurrassani said.

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