Reports coming out of Syria suggest that a recent US airstrike against the town of al-Bab, an ISIS-held town near the Turkish border, killed a large number of innocent civilians, with estimates floating around 50.

The strike happened two weeks ago, and the US warplanes leveled a building ISIS was using as a makeshift prison, burying scores of detainees within. Bodies were still being recovered days later.

Centcom initially didn’t report the airstrike at all, but finally confirmed it this weekend, dubbing the jail an “ISIS headquarters” and saying they didn’t see any of the evidence of civilian deaths.

Centcom had previously conceded they were investigating a handful of the reports of civilian deaths in the air war against ISIS, but hadn’t confirmed any of them. Given they were talking about only a handful of casualties, this was clearly not among the incidents being investigated at the time.