Officials said they did not know who was behind the attack.

It was not clear what forces were behind the attack.

One in four people said they did not know who was behind the attacks.

However, the Taliban have said they were behind the attack.

But the group has been behind numerous attacks since then.

She asks him to help find out who was behind the attacks.

Nor is there evidence that any particular group has been behind the attacks.

We think the people behind the attacks today may have something else planned.

I do hope he finds out soon who is behind the attacks.

Officials say they are still uncertain who was behind the attack.