A day after Israeli forces bombed a U.N. school complex in central Gaza that had become a shelter for displaced Palestinians, some of the facts remain unclear or under contention.

Israel said it struck three classrooms used by 20 to 30 Palestinian militants, including some who participated in the Oct. 7 Hamas-led attack on Israel, and that it was unaware of civilian casualties. Gazan health authorities said that among the dozens of people killed, many were children and women. Here is what we know and do not know.

What was bombed?

The multistory building was one of several that made up the UNRWA Nuseirat Boys’ Preparatory School. It was one of the many schools in Gaza run by the main U.N. agency for Palestinian refugees and their descendants.

Like all of the territory’s schools, it stopped operating as a school in October, after Hamas led an assault on Israel, and Israel began its retaliatory bombing campaign. And like many of them, it became crowded with people who, displaced by the war from homes in other parts of Gaza, sought shelter in schools, hospitals and other institutions they hoped would be less likely to be bombed.

Philippe Lazzarini, the director of the U.N. aid agency for Palestinian refugees, said 6,000 people had been living in the school. About three-quarters of Gaza’s roughly 2.2 million people have fled their homes, many of them multiple times.

The Israeli military has referred to the school in Nuseirat as a militant base, saying that fighters for Hamas and Palestinian Islamic Jihad used three of its classrooms to plan and conduct operations against Israel.