At least two of the 44 people killed in Tuesday’s airstrike on a migrant detention center in Libya were set to leave the country in the coming days, the International Organization for Migration said on Wednesday.

In addition to the two killed, more than 180 others staying in the same detention center were registered to return to their home countries through the U.N. agency’s voluntary migrant return program, which helps arrange their documents and transport, the organization said. In recent years, IOM has moved around 40,000 migrants out of Libya through the same program.

“Two of the dead were scheduled to leave as soon as this week,” said Joel Millman, a senior press officer at IOM.

The airstrike on the Tajoura center, where around 600 people were being held, came less than two months after another airstrike landed less than 100 meters from the center, injuring two people.

At the time, the U.N. refugee agency urged Libyan authorities to move the detainees, warning they were at urgent risk as violence between armed groups continues to escalate in Libya.

But they were never released or transferred. On Tuesday night, the facility was hit directly. In addition to the 44 killed, more than 100 others were injured.

For refugee advocates, the incident illustrated the most serious danger of turning asylum seekers away from Europe and returning them to detention centers in a conflict zone, which has happened more frequently in recent years as the European Union worked with the Libyan coast guard to reduce Mediterranean crossings. Libyan authorities often intercept Europe-bound ships and dinghies carrying migrants and return them to Libya. According to the U.N., more than 3,000 asylum seekers currently being held in Libya are at risk of falling victim to violence there, especially as clashes have broken out in Tripoli since April.

“For those who think return to Libya is an option, what we have to understand is that people in this detention center were killed by the very same violence that they were prevented from fleeing,” said Charlie Yaxley, spokesperson for the Mediterranean and Libya at the U.N. High Commissioner for Refugees. “The reason people were trying to flee Libya is because they weren’t safe.”

The two killed Tuesday just before they were set to return home had likely embarked on a lengthy, dangerous journey that led them to Libya in the first place.

Most of the migrants being held in the Libyan centers are from sub-Saharan Africa and face enormous risk when they leave home and head north, often with the hopes they will board a boat or dinghy in Libya and eventually reach Europe. The journey can take months or years.

They crisscross the continent on foot or piled into backs of trucks, risking their lives moving across the Saharan desert. Along the way, they are extorted, assaulted and often held against their will by human smugglers who profit off their desperation. Women face the risk of rape and forced prostitution. Men and children can be forced into hard labor.

And all of that can happen before they ever reach Libya, at which point they face huge risks again aboard boats headed to Europe, where Libyan authorities can intercept and detain them, or they can drown at sea.

Those brought back to Libya often find themselves languishing in dangerous detention centers, where disease is rife and the threat of violence looms constantly. Even before an airstrike hit Tajoura this week, advocates were concerned about migrants staying in such conditions.

“Some centers look like some of the worst places you might find yourself in on the journey,” Yaxley said.

In a statement on Wednesday, Prince Alfani, Doctors Without Borders’ Libya medical coordinator said that a team had visited the center earlier on Tuesday and saw 600 people trapped there, including many who now fear for their lives, after a number of incidents occurred before the deadly airstrike on Tuesday.

“Just eight weeks ago in Tajoura detention center, shrapnel from a blast tore through the roof of the women’s room and nearly hit an infant,” he said.

No one has taken responsibility for Tuesday’s airstrike, but the U.N.-backed Libyan government blamed forces loyal to Khalifa Hifter, a Libyan commander who has been clashing with the government in Tripoli since April.

Ghassan Salama, head of the U.N. mission in Libya, said in a statement that “[t]his attack clearly could constitute a war crime, as it killed by surprise innocent people whose dire conditions forced them to be in that shelter."

UNHCR and the IOM said in a joint statement that the “coordinates of such centers in Tripoli are well known to combatants, who also know those detained at Tajoura are civilians."

But even now, thousands of other civilians stuck inside Libyan detention centers remain at risk. And more than 200 of them are still being held inside Tajoura, the same center that was struck on Tuesday night.