The Saudi-led coalition fighting Houthi rebels in Yemen acknowledges “mistakes” were made in last month’s deadly airstrike on a school bus in northern Yemen, the Saudi Press Agency said Saturday.

The attack killed 51 people, including 40 children, according to the Houthi-held Health Ministry. The coalition cited “mistakes in compliance to the rules of engagement.”

In a statement, the command issued “regret over the mistakes, extends its sympathies and solidarity to the families of the victims.” It issued its conclusions after reviewing the findings of an assessment team.

“The Joint Forces Command will, as soon as the official findings are received, undertake legal proceedings to hold the ones who committed mistakes accountable according to the rules and regulations related to such cases,” the coalition said.

It added that it will “continue to revise and enhance its rules of engagement according to operational lessons learned, in a manner that guarantees non-recurrence of such incidents.”

CNN established that the bomb that hit the school bus on August 9 and killed dozens of children was US-made and had been sold to Saudi Arabia as part of a State Department-sanctioned arms deal.

The explosive was found by CNN to be an American-made, 500-pound (227-kilogram), laser-guided MK 82 bomb, a weapon similar to one that killed 155 people in an October 2016 attack on a funeral hall in Yemen.