Poland illegally pushed back a group of migrants camped out on its border with Belarus in late August.
Analysis of satellite imagery and other photos and videos by NGO Amnesty International, published on Thursday (September 30) revealed the incident.
Amnesty said that the imagery from August 18th helped it detect the movement of the migrant group from Polish territory back to Belarusian territory.
The information has shed new light on their case, which has been tough for NGOs and media to cover, amid an ongoing state of emergency along the border.
Here's the director of Amnesty International's European Institutions office, Eve Geddie.
"Forcing people back who are trying to claim asylum without an individual assessment of their protection needs is against European and international law. So Poland has an obligation to assess these people and see what their needs are and if they need to be given refugee status in Poland."
Poland, Lithuania and Latvia have reported sharp increases in migrants from countries like Afghanistan and Iraq trying to cross their borders from Belarus.
Warsaw and Brussels have called it a form of hybrid warfare, designed to put pressure on the EU over sanctions it imposed on Minsk.
Human rights groups have also accused Poland's nationalist government of failure to provide adequate support and conditions for those trying to cross.
"Poland has been cruelly holding this group at the border for weeks now, and the dire conditions there are just worsening every day. People are without shelter in increasingly poor temperatures and we're entering now the winter period, so this is extremely concerning for us and we have to be clear as well, the dire situation faced by this group now is one entirely of the Polish government's making, because they're not admitting them to the territory and not giving them the protection and shelter that they need."
Three migrants died on the Polish side of the border, and another just inside Belarus earlier this month while trying to cross into Poland.
The causes of their deaths have not been given.
A fifth death of an Iraqi man just inside Poland, likely from a heart attack, was also reported.
Last week, the EU executive urged Warsaw to protect human lives and allow the bloc's joint frontier force, Frontex, to provide assistance.